def hdf2ds(fnames):
    """Load dataset(s) from an HDF5 file

    Parameters
    ----------
    fname : list(str)
      Names of the input HDF5 files

    Returns
    -------
    list(Dataset)
      All datasets-like elements in all given HDF5 files (in order of
      appearance). If any given HDF5 file contains non-Dataset elements
      they are silently ignored. If no given HDF5 file contains any
      dataset, an empty list is returned.
    """
    from mvpa2.base.hdf5 import h5load
    dss = []
    for fname in fnames:
        content = h5load(fname)
        if is_datasetlike(content):
            dss.append(content)
        else:
            for c in content:
                if is_datasetlike(c):
                    dss.append(c)
    return dss

    def forward(self, data):
        """Map data from input to output space.

        Parameters
        ----------
        data : Dataset-like, (at least 2D)-array-like
          Typically this is a `Dataset`, but it might also be a plain data
          array, or even something completely different(TM) that is supported
          by a subclass' implementation. If such an object is Dataset-like it
          is handled by a dedicated method that also transforms dataset
          attributes if necessary. If an array-like is passed, it has to be
          at least two-dimensional, with the first axis separating samples
          or observations. For single samples `forward1()` might be more
          appropriate.
        """
        if is_datasetlike(data):
            if __debug__:
                debug('MAP', "Forward-map %s-shaped dataset through '%s'."
                        % (data.shape, self))
            return self._forward_dataset(data)
        else:
            if hasattr(data, 'ndim') and data.ndim < 2:
                raise ValueError(
                    'Mapper.forward() only support mapping of data with '
                    'at least two dimensions, where the first axis '
                    'separates samples/observations. Consider using '
                    'Mapper.forward1() instead.')
            if __debug__:
                debug('MAP', "Forward-map data through '%s'." % (self))
            return self._forward_data(data)

    def train(self, ds):
        """
        The default implementation calls ``_pretrain()``, ``_train()``, and
        finally ``_posttrain()``.

        Parameters
        ----------
        ds: Dataset
          Training dataset.

        Returns
        -------
        None
        """
        got_ds = is_datasetlike(ds)

        # TODO remove first condition if all Learners get only datasets
        if got_ds and (ds.nfeatures == 0 or len(ds) == 0):
            raise DegenerateInputError(
                "Cannot train learner on degenerate data %s" % ds)
        if __debug__:
            debug(
                "LRN",
                "Training learner %(lrn)s on dataset %(dataset)s",
                msgargs={'lrn': self, 'dataset': ds})

        self._pretrain(ds)

        # remember the time when started training
        t0 = time.time()

        if got_ds:
            # things might have happened during pretraining
            if ds.nfeatures > 0:
                self._train(ds)
            else:
                warning("Trying to train on dataset with no features present")
                if __debug__:
                    debug("LRN",
                          "No features present for training, no actual training "
                          "is called")
        else:
            # in this case we claim to have no idea and simply try to train
            self._train(ds)

        # store timing
        self.ca.training_time = time.time() - t0

        # and post-proc
        self._posttrain(ds)

        # finally flag as trained
        self._set_trained()

        if __debug__:
            debug(
                "LRN",
                "Finished training learner %(lrn)s on dataset %(dataset)s",
                msgargs={'lrn': self, 'dataset': ds})

    def compute(self, ds1, ds2=None):
        """Generic computation of any kernel

        Assumptions:

         - ds1, ds2 are either datasets or arrays,
         - presumably 2D (not checked neither enforced here
         - _compute takes ndarrays. If your kernel needs datasets,
           override compute
        """
        if is_datasetlike(ds1):
            ds1 = ds1.samples
        if ds2 is None:
            ds2 = ds1
        elif is_datasetlike(ds2):
            ds2 = ds2.samples
        # TODO: assure 2D shape
        self._compute(ds1, ds2)

    def _sl_call(self, dataset, roi_ids, nproc):
        """Classical generic searchlight implementation
        """
        assert(self.results_backend in ('native', 'hdf5'))
        # compute
        if nproc is not None and nproc > 1:
            # split all target ROIs centers into `nproc` equally sized blocks
            nproc_needed = min(len(roi_ids), nproc)
            nblocks = nproc_needed \
                      if self.nblocks is None else self.nblocks
            roi_blocks = np.array_split(roi_ids, nblocks)

            # the next block sets up the infrastructure for parallel computing
            # this can easily be changed into a ParallelPython loop, if we
            # decide to have a PP job server in PyMVPA
            import pprocess
            p_results = pprocess.Map(limit=nproc_needed)
            if __debug__:
                debug('SLC', "Starting off %s child processes for nblocks=%i"
                      % (nproc_needed, nblocks))
            compute = p_results.manage(
                        pprocess.MakeParallel(self._proc_block))
            for iblock, block in enumerate(roi_blocks):
                # should we maybe deepcopy the measure to have a unique and
                # independent one per process?
                seed = mvpa2.get_random_seed()
                compute(block, dataset, copy.copy(self.__datameasure),
                        seed=seed, iblock=iblock)
        else:
            # otherwise collect the results in an 1-item list
            p_results = [
                    self._proc_block(roi_ids, dataset, self.__datameasure)]

        # Finally collect and possibly process results
        # p_results here is either a generator from pprocess.Map or a list.
        # In case of a generator it allows to process results as they become
        # available
        result_ds = self.results_fx(sl=self,
                                    dataset=dataset,
                                    roi_ids=roi_ids,
                                    results=self.__handle_all_results(p_results))

        # Assure having a dataset (for paranoid ones)
        if not is_datasetlike(result_ds):
            try:
                result_a = np.atleast_1d(result_ds)
            except ValueError, e:
                if 'setting an array element with a sequence' in str(e):
                    # try forcing object array.  Happens with
                    # test_custom_results_fx_logic on numpy 1.4.1 on Debian
                    # squeeze
                    result_a = np.array(result_ds, dtype=object)
                else:
                    raise
            result_ds = Dataset(result_a)

    def _proc_block(self, block, ds, measure):
        """Little helper to capture the parts of the computation that can be
        parallelized
        """
        if __debug__:
            debug_slc_ = 'SLC_' in debug.active
            debug('SLC',
                  "Starting computing block for %i elements" % len(block))
        if self.ca.is_enabled('roi_sizes'):
            roi_sizes = []
        else:
            roi_sizes = None
        results = []
        # put rois around all features in the dataset and compute the
        # measure within them
        for i, f in enumerate(block):
            # retrieve the feature ids of all features in the ROI from the query
            # engine
            roi_fids = self._queryengine[f]

            if __debug__ and  debug_slc_:
                debug('SLC_', 'For %r query returned ids %r' % (f, roi_fids))

            # slice the dataset
            roi = ds[:, roi_fids]

            if self.__add_center_fa:
                # add fa to indicate ROI seed if requested
                roi_seed = np.zeros(roi.nfeatures, dtype='bool')
                roi_seed[roi_fids.index(f)] = True
                roi.fa[self.__add_center_fa] = roi_seed

            # compute the datameasure and store in results
            res = measure(roi)
            if self.ca.is_enabled('roi_feature_ids'):
                if not is_datasetlike(res):
                    res = Dataset(np.atleast_1d(res))
                # add roi feature ids to intermediate result dataset for later
                # aggregation
                res.a['roi_feature_ids'] = roi_fids
            results.append(res)

            # store the size of the roi dataset
            if not roi_sizes is None:
                roi_sizes.append(roi.nfeatures)

            if __debug__:
                debug('SLC', "Doing %i ROIs: %i (%i features) [%i%%]" \
                    % (len(block),
                       f+1,
                       roi.nfeatures,
                       float(i+1)/len(block)*100,), cr=True)

        return results, roi_sizes

 def _get_sl_connectomes(self, seed_means, qe_all, datasets, inode, connectivity_mapper):
     # For each SL, computing connectivity of features to seed means
     sl_connectomes = []
     # Looping over each subject
     for seed_mean, qe_, sd in zip(seed_means, qe_all, datasets):
         connectivity_mapper.train(seed_mean)
         sl_ids = qe_[inode]
         if is_datasetlike(sl_ids):
             assert (sl_ids.nsamples == 1)
             sl_ids = sl_ids.samples[0, :].tolist()
         sl_connectomes.append(connectivity_mapper.forward(sd[:, sl_ids]))
     return sl_connectomes

 def _predict(self, data):
     l = len(self._ulabels)
     # oh those lovely random estimates, for now just an estimate
     # per sample. Since we are random after all -- keep it random
     self.ca.estimates = np.random.normal(size=len(data))
     if is_datasetlike(data) and self.params.same:
         # decide on mapping between original labels
         labels_map = dict(
             (t, rt) for t, rt in zip(self._ulabels,
                                      self._ulabels[npr.randint(0, l, size=l)]))
         return [labels_map[t] for t in data.sa[self.get_space()].value]
     else:
         # random one per each
         return self._ulabels[npr.randint(0, l, size=len(data))]

def hstack(datasets):
    """Stacks datasets horizontally (appending features).

    Sample attribute collections are merged incrementally, attribute with
    identical keys overwriting previous ones in the stacked dataset. All
    datasets must have an identical set of feature attributes (matching keys,
    not values), otherwise a ValueError will be raised.
    No dataset attributes from any source dataset will be transferred into the
    stacked dataset.

    Parameters
    ----------
    datasets : tuple
      Sequence of datasets to be stacked.

    Returns
    -------
    AttrDataset (or respective subclass)
    """
    #
    # XXX Use CombinedMapper in here whenever it comes back
    #

    # fall back to numpy if it is not a dataset
    if not is_datasetlike(datasets[0]):
        # we might get a list of 1Ds that would yield wrong results when
        # turned into a dict (would run along samples-axis)
        return AttrDataset(np.atleast_2d(np.hstack(datasets)))

    if __debug__:
        target = sorted(datasets[0].fa.keys())
        if not np.all([sorted(ds.fa.keys()) == target for ds in datasets]):
            raise ValueError("Feature attributes collections of to be stacked "
                             "datasets have varying attributes.")
    # will puke if not equal number of samples
    stacked_samp = np.concatenate([ds.samples for ds in datasets], axis=1)

    stacked_fa = {}
    for attr in datasets[0].fa:
        stacked_fa[attr] = np.concatenate(
            [ds.fa[attr].value for ds in datasets], axis=0)
    # create the dataset
    merged = datasets[0].__class__(stacked_samp, fa=stacked_fa)

    for ds in datasets:
        merged.sa.update(ds.sa)

    return merged

def vstack(datasets):
    """Stacks datasets vertically (appending samples).

    Feature attribute collections are merged incrementally, attribute with
    identical keys overwriting previous ones in the stacked dataset. All
    datasets must have an identical set of sample attributes (matching keys,
    not values), otherwise a ValueError will be raised.
    No dataset attributes from any source dataset will be transferred into the
    stacked dataset. If all input dataset have common dataset attributes that
    are also valid for the stacked dataset, they can be moved into the output
    dataset like this::

      ds_merged = vstack((ds1, ds2, ds3))
      ds_merged.a.update(ds1.a)

    Parameters
    ----------
    datasets : tuple
      Sequence of datasets to be stacked.

    Returns
    -------
    AttrDataset (or respective subclass)
    """
    # fall back to numpy if it is not a dataset
    if not is_datasetlike(datasets[0]):
        return AttrDataset(np.vstack(datasets))

    if __debug__:
        target = sorted(datasets[0].sa.keys())
        if not np.all([sorted(ds.sa.keys()) == target for ds in datasets]):
            raise ValueError("Sample attributes collections of to be stacked "
                             "datasets have varying attributes.")
    # will puke if not equal number of features
    stacked_samp = np.concatenate([ds.samples for ds in datasets], axis=0)

    stacked_sa = {}
    for attr in datasets[0].sa:
        stacked_sa[attr] = np.concatenate(
            [ds.sa[attr].value for ds in datasets], axis=0)
    # create the dataset
    merged = datasets[0].__class__(stacked_samp, sa=stacked_sa)

    for ds in datasets:
        merged.fa.update(ds.fa)

    return merged

    def _posttrain(self, dataset):
        """Functionality post training

        For instance -- computing confusion matrix.

        Parameters
        ----------
        dataset : Dataset
          Data which was used for training
        """
        super(Classifier, self)._posttrain(dataset)

        ca = self.ca

        # needs to be assigned first since below we use predict
        self.__trainednfeatures = dataset.nfeatures

        if __debug__ and 'CHECK_TRAINED' in debug.active:
            self.__trainedidhash = dataset.idhash

        if ca.is_enabled('training_stats') and \
               not ca.is_set('training_stats'):
            # we should not store predictions for training data,
            # it is confusing imho (yoh)
            ca.change_temporarily(
                disable_ca=["predictions"])
            if self.params.retrainable:
                # we would need to recheck if data is the same,
                # XXX think if there is a way to make this all
                # efficient. For now, probably, retrainable
                # classifiers have no chance but not to use
                # training_stats... sad
                self.__changedData_isset = False
            predictions = self.predict(dataset)
            ca.reset_changed_temporarily()
            targets = dataset.sa[self.get_space()].value
            if is_datasetlike(predictions) and (self.get_space() in predictions.fa):
                # e.g. in case of pair-wise uncombined results - provide
                # stats per each of the targets pairs
                prediction_targets = predictions.fa[self.get_space()].value
                ca.training_stats = dict(
                    (t, self.__summary_class__(
                        targets=targets, predictions=predictions.samples[:, i]))
                    for i, t in enumerate(prediction_targets))
            else:
                ca.training_stats = self.__summary_class__(
                    targets=targets, predictions=predictions)

    def reverse(self, data):
        """Reverse-map data from output back into input space.

        Parameters
        ----------
        data : Dataset-like, anything
          Typically this is a `Dataset`, but it might also be a plain data
          array, or even something completely different(TM) that is supported
          by a subclass' implementation. If such an object is Dataset-like it
          is handled by a dedicated method that also transforms dataset
          attributes if necessary.
        """
        if is_datasetlike(data):
            if __debug__:
                debug('MAP', "Reverse-map %s-shaped dataset through '%s'."
                        % (data.shape, self))
            return self._reverse_dataset(data)
        else:
            if __debug__:
                debug('MAP', "Reverse-map data through '%s'." % (self))
            return self._reverse_data(data)

    def p(self, x, return_tails=False, **kwargs):
        """Returns the p-value for values of `x`.
        Returned values are determined left, right, or from any tail
        depending on the constructor setting.

        In case a `FeaturewiseMeasure` was used to estimate the
        distribution the method returns an array. In that case `x` can be
        a scalar value or an array of a matching shape.
        """
        peas = _pvalue(x, self.cdf, self.__tail, return_tails=return_tails, **kwargs)
        if is_datasetlike(x):
            # return the p-values in a dataset as well and assign the input
            # dataset attributes to the return dataset too
            pds = x.copy(deep=False)
            if return_tails:
                pds.samples = peas[0]
                return pds, peas[1]
            else:
                pds.samples = peas
                return pds
        return peas

    def _get_hypesvs(self, sl_connectomes, local_common_model=None):
        '''
        Hyperalign connectomes and return mapppers
        and trained SVDMapper of common space.

        Parameters
        ----------
        sl_connectomes: a list of connectomes to hyperalign
        local_common_model: a reference common model to be used.

        Returns
        -------
        a tuple (sl_hmappers, svm, local_common_model)
        sl_hmappers: a list of mappers corresponding to input list in that order.
        svm: a svm mapper based on the input data. if given a common model, this is None.
        local_common_model: If local_common_model is provided as input, this will be None.
            Otherwise, local_common_model will be computed here and returned.
        '''
        # TODO Should we z-score sl_connectomes?
        return_model = False if self.params.save_model is None else True
        if local_common_model is not None:
            ha = Hyperalignment(level2_niter=0)
            if not is_datasetlike(local_common_model):
                local_common_model = Dataset(samples=local_common_model)
            ha.train([local_common_model])
            sl_hmappers = ha(sl_connectomes)
            return sl_hmappers, None, None
        ha = Hyperalignment()
        sl_hmappers = ha(sl_connectomes)
        sl_connectomes = [slhm.forward(slc) for slhm, slc in zip(sl_hmappers, sl_connectomes)]
        _ = [zscore(slc, chunks_attr=None) for slc in sl_connectomes]
        sl_connectomes = np.dstack(sl_connectomes).mean(axis=-1)
        svm = SVDMapper(force_train=True)
        svm.train(sl_connectomes)
        if return_model:
            local_common_model = svm.forward(sl_connectomes)
        else:
            local_common_model = None
        return sl_hmappers, svm, local_common_model

def hstack(datasets, a=None):
    """Stacks datasets horizontally (appending features).

    Sample attribute collections are merged incrementally, attribute with
    identical keys overwriting previous ones in the stacked dataset. All
    datasets must have an identical set of feature attributes (matching keys,
    not values), otherwise a ValueError will be raised.
    No dataset attributes from any source dataset will be transferred into the
    stacked dataset.

    Parameters
    ----------
    datasets : tuple
        Sequence of datasets to be stacked.
    a: {'unique','drop_nonunique','uniques','all'} or True or False or None (default: None)
        Indicates which dataset attributes from datasets are stored
        in merged_dataset. If an int k, then the dataset attributes from
        datasets[k] are taken. If 'unique' then it is assumed that any
        attribute common to more than one dataset in datasets is unique;
        if not an exception is raised. If 'drop_nonunique' then as 'unique',
        except that exceptions are not raised. If 'uniques' then, for each
        attribute,  any unique value across the datasets is stored in a tuple
        in merged_datasets. If 'all' then each attribute present in any
        dataset across datasets is stored as a tuple in merged_datasets;
        missing values are replaced by None. If None (the default) then no
        attributes are stored in merged_dataset. True is equivalent to
        'drop_nonunique'. False is equivalent to None.

    Returns
    -------
    AttrDataset (or respective subclass)
    """
    #
    # XXX Use CombinedMapper in here whenever it comes back
    #

    if not len(datasets):
        raise ValueError('concatenation of zero-length sequences is impossible')
    if not len(datasets) > 1:
        # trivial hstack
        return datasets[0]
    # fall back to numpy if it is not a dataset
    if not is_datasetlike(datasets[0]):
        # we might get a list of 1Ds that would yield wrong results when
        # turned into a dict (would run along samples-axis)
        return AttrDataset(np.atleast_2d(np.hstack(datasets)))

    if __debug__:
        target = sorted(datasets[0].fa.keys())
        if not np.all([sorted(ds.fa.keys()) == target for ds in datasets]):
            raise ValueError("Feature attributes collections of to be stacked "
                             "datasets have varying attributes.")
    # will puke if not equal number of samples
    stacked_samp = np.concatenate([ds.samples for ds in datasets], axis=1)

    stacked_fa = {}
    for attr in datasets[0].fa:
        stacked_fa[attr] = np.concatenate(
            [ds.fa[attr].value for ds in datasets], axis=0)
    # create the dataset
    merged = datasets[0].__class__(stacked_samp, fa=stacked_fa)

    for ds in datasets:
        merged.sa.update(ds.sa)

    _stack_add_equal_dataset_attributes(merged, datasets, a)

    return merged

def vstack(datasets, a=None):
    """Stacks datasets vertically (appending samples).

    Feature attribute collections are merged incrementally, attribute with
    identical keys overwriting previous ones in the stacked dataset. All
    datasets must have an identical set of sample attributes (matching keys,
    not values), otherwise a ValueError will be raised.
    No dataset attributes from any source dataset will be transferred into the
    stacked dataset. If all input dataset have common dataset attributes that
    are also valid for the stacked dataset, they can be moved into the output
    dataset like this::

      ds_merged = vstack((ds1, ds2, ds3))
      ds_merged.a.update(ds1.a)

    Parameters
    ----------
    datasets : tuple
        Sequence of datasets to be stacked.
    a: {'unique','drop_nonunique','uniques','all'} or True or False or None (default: None)
        Indicates which dataset attributes from datasets are stored
        in merged_dataset. If an int k, then the dataset attributes from
        datasets[k] are taken. If 'unique' then it is assumed that any
        attribute common to more than one dataset in datasets is unique;
        if not an exception is raised. If 'drop_nonunique' then as 'unique',
        except that exceptions are not raised. If 'uniques' then, for each
        attribute,  any unique value across the datasets is stored in a tuple
        in merged_datasets. If 'all' then each attribute present in any
        dataset across datasets is stored as a tuple in merged_datasets;
        missing values are replaced by None. If None (the default) then no
        attributes are stored in merged_dataset. True is equivalent to
        'drop_nonunique'. False is equivalent to None.

    Returns
    -------
    AttrDataset (or respective subclass)
    """
    if not len(datasets):
        raise ValueError('concatenation of zero-length sequences is impossible')
    if not len(datasets) > 1:
        # trivial vstack
        return datasets[0]
    # fall back to numpy if it is not a dataset
    if not is_datasetlike(datasets[0]):
        return AttrDataset(np.vstack(datasets))

    if __debug__:
        target = sorted(datasets[0].sa.keys())
        if not np.all([sorted(ds.sa.keys()) == target for ds in datasets]):
            raise ValueError("Sample attributes collections of to be stacked "
                             "datasets have varying attributes.")
    # will puke if not equal number of features
    stacked_samp = np.concatenate([ds.samples for ds in datasets], axis=0)

    stacked_sa = {}
    for attr in datasets[0].sa:
        stacked_sa[attr] = np.concatenate(
            [ds.sa[attr].value for ds in datasets], axis=0)
    # create the dataset
    merged = datasets[0].__class__(stacked_samp, sa=stacked_sa)

    for ds in datasets:
        merged.fa.update(ds.fa)

    _stack_add_equal_dataset_attributes(merged, datasets, a)
    return merged

    def _train(self, source):
        params = self.params
        # Since it is unsupervised, we don't care about labels
        datas = ()
        odatas = ()
        means = ()
        shapes = ()

        assess_residuals = __debug__ and 'MAP_' in debug.active

        target = source.sa[self.get_space()].value

        for i, ds in enumerate((source, target)):
            if is_datasetlike(ds):
                data = np.asarray(ds.samples)
            else:
                data = ds
            if assess_residuals:
                odatas += (data,)
            if self._demean:
                if i == 0:
                    mean = self._offset_in
                else:
                    mean = data.mean(axis=0)
                data = data - mean
            else:
                # no demeaning === zero means
                mean = np.zeros(shape=data.shape[1:])
            means += (mean,)
            datas += (data,)
            shapes += (data.shape,)

        # shortcuts for sizes
        sn, sm = shapes[0]
        tn, tm = shapes[1]

        # Check the sizes
        if sn != tn:
            raise ValueError, "Data for both spaces should have the same " \
                  "number of samples. Got %d in source and %d in target space" \
                  % (sn, tn)

        # Sums of squares
        ssqs = [np.sum(d**2, axis=0) for d in datas]

        # XXX check for being invariant?
        #     needs to be tuned up properly and not raise but handle
        for i in xrange(2):
            if np.all(ssqs[i] <= np.abs((np.finfo(datas[i].dtype).eps
                                       * sn * means[i] )**2)):
                raise ValueError, "For now do not handle invariant in time datasets"

        norms = [ np.sqrt(np.sum(ssq)) for ssq in ssqs ]
        normed = [ data/norm for (data, norm) in zip(datas, norms) ]

        # add new blank dimensions to source space if needed
        if sm < tm:
            normed[0] = np.hstack( (normed[0], np.zeros((sn, tm-sm))) )

        if sm > tm:
            if params.reduction:
                normed[1] = np.hstack( (normed[1], np.zeros((sn, sm-tm))) )
            else:
                raise ValueError, "reduction=False, so mapping from " \
                      "higher dimensionality " \
                      "source space is not supported. Source space had %d " \
                      "while target %d dimensions (features)" % (sm, tm)

        source, target = normed
        if params.oblique:
            # Just do silly linear system of equations ;) or naive
            # inverse problem
            if sn == sm and tm == 1:
                T = np.linalg.solve(source, target)
            else:
                T = np.linalg.lstsq(source, target, rcond=params.oblique_rcond)[0]
            ss = 1.0
        else:
            # Orthogonal transformation
            # figure out optimal rotation
            if params.svd == 'numpy':
                U, s, Vh = np.linalg.svd(np.dot(target.T, source),
                               full_matrices=False)
            elif params.svd == 'scipy':
                # would raise exception if not present
                externals.exists('scipy', raise_=True)
                import scipy
                U, s, Vh = scipy.linalg.svd(np.dot(target.T, source),
                               full_matrices=False)
            elif params.svd == 'dgesvd':
                from mvpa2.support.lapack_svd import svd as dgesvd
                U, s, Vh = dgesvd(np.dot(target.T, source),
                                    full_matrices=True, algo='svd')
            else:
                raise ValueError('Unknown type of svd %r'%(params.svd))
            T = np.dot(Vh.T, U.T)

            if not params.reflection:
                # then we need to assure that it is only rotation
                # "recipe" from
#.........这里部分代码省略.........

 def wrap_samples(obj, data, *args, **kwargs):
     if is_datasetlike(data):
         return fx(obj, data, *args, **kwargs)
     else:
         return fx(obj, Dataset(data), *args, **kwargs)

def test_from_wizard():
    samples = np.arange(12).reshape((4, 3)).view(myarray)
    labels = range(4)
    chunks = [1, 1, 2, 2]

    ds = Dataset(samples, sa={'targets': labels, 'chunks': chunks})
    ds.init_origids('both')
    first = ds.sa.origids
    # now do again and check that they get regenerated
    ds.init_origids('both')
    assert_false(first is ds.sa.origids)
    assert_array_equal(first, ds.sa.origids)

    ok_(is_datasetlike(ds))
    ok_(not is_datasetlike(labels))

    # array subclass survives
    ok_(isinstance(ds.samples, myarray))

    ## XXX stuff that needs thought:

    # ds.sa (empty) has this in the public namespace:
    #   add, get, getvalue, has_key, is_set, items, listing, name, names
    #   owner, remove, reset, setvalue, which_set
    # maybe we need some form of leightweightCollection?

    assert_array_equal(ds.samples, samples)
    assert_array_equal(ds.sa.targets, labels)
    assert_array_equal(ds.sa.chunks, chunks)

    # same should work for shortcuts
    assert_array_equal(ds.targets, labels)
    assert_array_equal(ds.chunks, chunks)

    ok_(sorted(ds.sa.keys()) == ['chunks', 'origids', 'targets'])
    ok_(sorted(ds.fa.keys()) == ['origids'])
    # add some more
    ds.a['random'] = 'blurb'

    # check stripping attributes from a copy
    cds = ds.copy() # full copy
    ok_(sorted(cds.sa.keys()) == ['chunks', 'origids', 'targets'])
    ok_(sorted(cds.fa.keys()) == ['origids'])
    ok_(sorted(cds.a.keys()) == ['random'])
    cds = ds.copy(sa=[], fa=[], a=[]) # plain copy
    ok_(cds.sa.keys() == [])
    ok_(cds.fa.keys() == [])
    ok_(cds.a.keys() == [])
    cds = ds.copy(sa=['targets'], fa=None, a=['random']) # partial copy
    ok_(cds.sa.keys() == ['targets'])
    ok_(cds.fa.keys() == ['origids'])
    ok_(cds.a.keys() == ['random'])

    # there is not necessarily a mapper present
    ok_(not ds.a.has_key('mapper'))

    # has to complain about misshaped samples attributes
    assert_raises(ValueError, Dataset.from_wizard, samples, labels + labels)

    # check that we actually have attributes of the expected type
    ok_(isinstance(ds.sa['targets'], ArrayCollectable))

    # the dataset will take care of not adding stupid stuff
    assert_raises(ValueError, ds.sa.__setitem__, 'stupid', np.arange(3))
    assert_raises(ValueError, ds.fa.__setitem__, 'stupid', np.arange(4))
    # or change proper attributes to stupid shapes
    try:
        ds.sa.targets = np.arange(3)
    except ValueError:
        pass
    else:
        ok_(False, msg="Assigning value with improper shape to attribute "
                       "did not raise exception.")

    def _proc_block(self, block, ds, measure, seed=None, iblock='main'):
        """Little helper to capture the parts of the computation that can be
        parallelized

        Parameters
        ----------
        seed
          RNG seed.  Should be provided e.g. in child process invocations
          to guarantee that they all seed differently to not keep generating
          the same sequencies due to reusing the same copy of numpy's RNG
        block
          Critical for generating non-colliding temp filenames in case
          of hdf5 backend.  Otherwise RNGs of different processes might
          collide in their temporary file names leading to problems.
        """
        if seed is not None:
            mvpa2.seed(seed)
        if __debug__:
            debug_slc_ = 'SLC_' in debug.active
            debug('SLC',
                  "Starting computing block for %i elements" % len(block))
        results = []
        store_roi_feature_ids = self.ca.is_enabled('roi_feature_ids')
        store_roi_sizes = self.ca.is_enabled('roi_sizes')
        store_roi_center_ids = self.ca.is_enabled('roi_center_ids')

        assure_dataset = any([store_roi_feature_ids,
                              store_roi_sizes,
                              store_roi_center_ids])

        # put rois around all features in the dataset and compute the
        # measure within them
        for i, f in enumerate(block):
            # retrieve the feature ids of all features in the ROI from the query
            # engine
            roi_specs = self._queryengine[f]

            if __debug__ and  debug_slc_:
                debug('SLC_', 'For %r query returned roi_specs %r'
                      % (f, roi_specs))

            if is_datasetlike(roi_specs):
                # TODO: unittest
                assert(len(roi_specs) == 1)
                roi_fids = roi_specs.samples[0]
            else:
                roi_fids = roi_specs

            # slice the dataset
            roi = ds[:, roi_fids]

            if is_datasetlike(roi_specs):
                for n, v in roi_specs.fa.iteritems():
                    roi.fa[n] = v

            if self.__add_center_fa:
                # add fa to indicate ROI seed if requested
                roi_seed = np.zeros(roi.nfeatures, dtype='bool')
                if f in roi_fids:
                    roi_seed[roi_fids.index(f)] = True
                else:
                    warning("Center feature attribute id %s not found" % f)
                roi.fa[self.__add_center_fa] = roi_seed

            # compute the datameasure and store in results
            res = measure(roi)

            if assure_dataset and not is_datasetlike(res):
                res = Dataset(np.atleast_1d(res))
            if store_roi_feature_ids:
                # add roi feature ids to intermediate result dataset for later
                # aggregation
                res.a['roi_feature_ids'] = roi_fids
            if store_roi_sizes:
                res.a['roi_sizes'] = roi.nfeatures
            if store_roi_center_ids:
                res.a['roi_center_ids'] = f
            results.append(res)

            if __debug__:
                debug('SLC', "Doing %i ROIs: %i (%i features) [%i%%]" \
                    % (len(block),
                       f + 1,
                       roi.nfeatures,
                       float(i + 1) / len(block) * 100,), cr=True)

        if self.results_postproc_fx:
            if __debug__:
                debug('SLC', "Post-processing %d results in proc_block using %s"
                      % (len(results), self.results_postproc_fx))
            results = self.results_postproc_fx(results)
        if self.results_backend == 'native':
            pass                        # nothing special
        elif self.results_backend == 'hdf5':
            # store