def hint(self, index):
        """Adds a 'hint', telling Mongo the proper index to use for the query.

        Judicious use of hints can greatly improve query
        performance. When doing a query on multiple fields (at least
        one of which is indexed) pass the indexed field as a hint to
        the query. Hinting will not do anything if the corresponding
        index does not exist. Raises
        :class:`~pymongo.errors.InvalidOperation` if this cursor has
        already been used.

        `index` should be an index as passed to
        :meth:`~pymongo.collection.Collection.create_index`
        (e.g. ``[('field', ASCENDING)]``). If `index`
        is ``None`` any existing hints for this query are cleared. The
        last hint applied to this cursor takes precedence over all
        others.

        :Parameters:
          - `index`: index to hint on (as an index specifier)
        """
        self.__check_okay_to_chain()
        if index is None:
            self.__hint = None
            return self

        self.__hint = helpers._index_document(index)
        return self

    def __init__(self, collection, spec=None, fields=None, skip=0, limit=0,
                 timeout=True, snapshot=False, tailable=False, sort=None,
                 max_scan=None, as_class=None,
                 _sock=None, _must_use_master=False, _is_command=False):
        """Create a new cursor.

        Should not be called directly by application developers - see
        :meth:`~pymongo.collection.Collection.find` instead.

        .. mongodoc:: cursors
        """
        self.__id = None

        if spec is None:
            spec = {}

        if not isinstance(spec, dict):
            raise TypeError("spec must be an instance of dict")
        if not isinstance(skip, int):
            raise TypeError("skip must be an instance of int")
        if not isinstance(limit, int):
            raise TypeError("limit must be an instance of int")
        if not isinstance(timeout, bool):
            raise TypeError("timeout must be an instance of bool")
        if not isinstance(snapshot, bool):
            raise TypeError("snapshot must be an instance of bool")
        if not isinstance(tailable, bool):
            raise TypeError("tailable must be an instance of bool")

        if fields is not None:
            if not fields:
                fields = {"_id": 1}
            if not isinstance(fields, dict):
                fields = helpers._fields_list_to_dict(fields)

        if as_class is None:
            as_class = collection.database.connection.document_class

        self.__collection = collection
        self.__spec = spec
        self.__fields = fields
        self.__skip = skip
        self.__limit = limit
        self.__timeout = timeout
        self.__tailable = tailable
        self.__snapshot = snapshot
        self.__ordering = sort and helpers._index_document(sort) or None
        self.__max_scan = max_scan
        self.__explain = False
        self.__hint = None
        self.__as_class = as_class
        self.__socket = _sock
        self.__must_use_master = _must_use_master
        self.__is_command = _is_command

        self.__data = []
        self.__connection_id = None
        self.__retrieved = 0
        self.__killed = False

    def __set_hint(self, index):
        if index is None:
            self.__hint = None
            return

        if isinstance(index, string_type):
            self.__hint = index
        else:
            self.__hint = helpers._index_document(index)

    def __init__(self, keys, **kwargs):
        """Create an Index instance.

        For use with :meth:`~pymongo.collection.Collection.create_indexes`.

        Takes either a single key or a list of (key, direction) pairs.
        The key(s) must be an instance of :class:`basestring`
        (:class:`str` in python 3), and the direction(s) must be one of
        (:data:`~pymongo.ASCENDING`, :data:`~pymongo.DESCENDING`,
        :data:`~pymongo.GEO2D`, :data:`~pymongo.GEOHAYSTACK`,
        :data:`~pymongo.GEOSPHERE`, :data:`~pymongo.HASHED`,
        :data:`~pymongo.TEXT`).

        Valid options include, but are not limited to:

          - `name`: custom name to use for this index - if none is
            given, a name will be generated.
          - `unique`: if ``True`` creates a uniqueness constraint on the index.
          - `background`: if ``True`` this index should be created in the
            background.
          - `sparse`: if ``True``, omit from the index any documents that lack
            the indexed field.
          - `bucketSize`: for use with geoHaystack indexes.
            Number of documents to group together within a certain proximity
            to a given longitude and latitude.
          - `min`: minimum value for keys in a :data:`~pymongo.GEO2D`
            index.
          - `max`: maximum value for keys in a :data:`~pymongo.GEO2D`
            index.
          - `expireAfterSeconds`: <int> Used to create an expiring (TTL)
            collection. MongoDB will automatically delete documents from
            this collection after <int> seconds. The indexed field must
            be a UTC datetime or the data will not expire.
          - `partialFilterExpression`: A document that specifies a filter for
            a partial index.

        See the MongoDB documentation for a full list of supported options by
        server version.

        .. note:: `partialFilterExpression` requires server version **>= 3.2**

        :Parameters:
          - `keys`: a single key or a list of (key, direction)
            pairs specifying the index to create
          - `**kwargs` (optional): any additional index creation
            options (see the above list) should be passed as keyword
            arguments

        .. versionchanged:: 3.2
            Added partialFilterExpression to support partial indexes.
        """
        keys = _index_list(keys)
        if "name" not in kwargs:
            kwargs["name"] = _gen_index_name(keys)
        kwargs["key"] = _index_document(keys)
        self.__document = kwargs

    def create_index(self, key_or_list, unique=False, ttl=300):
        """Creates an index on this collection.

        Takes either a single key or a list of (key, direction) pairs.
        The key(s) must be an instance of :class:`basestring`, and the
        directions must be one of (:data:`~pymongo.ASCENDING`,
        :data:`~pymongo.DESCENDING`). Returns the name of the created
        index.

        To create a single key index on the key ``'mike'`` we just use
        a string argument:

        >>> my_collection.create_index("mike")

        For a `compound index`_ on ``'mike'`` descending and
        ``'eliot'`` ascending we need to use a list of tuples:

        >>> my_collection.create_index([("mike", pymongo.DESCENDING),
        ...                             ("eliot", pymongo.ASCENDING)])

        :Parameters:
          - `key_or_list`: a single key or a list of (key, direction)
            pairs specifying the index to create
          - `unique` (optional): should this index guarantee
            uniqueness?
          - `ttl` (optional): time window (in seconds) during which
            this index will be recognized by subsequent calls to
            :meth:`ensure_index` - see documentation for
            :meth:`ensure_index` for details

        .. seealso:: :meth:`ensure_index`

        .. _compound index: http://www.mongodb.org/display/DOCS/Indexes#Indexes-CompoundKeysIndexes

        .. mongodoc:: indexes
        """
        if not isinstance(key_or_list, (str, unicode, list)):
            raise TypeError("key_or_list must either be a single key "
                            "or a list of (key, direction) pairs")

        to_save = SON()
        keys = helpers._index_list(key_or_list)
        name = self._gen_index_name(keys)
        to_save["name"] = name
        to_save["ns"] = self.__full_name
        to_save["key"] = helpers._index_document(keys)
        to_save["unique"] = unique

        self.__database.connection._cache_index(self.__database.name,
                                                self.__name, name, ttl)

        self.__database.system.indexes.insert(to_save, manipulate=False,
                                              check_keys=False)
        return to_save["name"]

    def __init__(
        self,
        collection,
        spec,
        fields,
        skip,
        limit,
        slave_okay,
        timeout,
        tailable,
        snapshot=False,
        sort=None,
        max_scan=None,
        _sock=None,
        _must_use_master=False,
        _is_command=False,
    ):
        """Create a new cursor.

        Should not be called directly by application developers - see
        :meth:`~pymongo.collection.Collection.find` instead.

        .. mongodoc:: cursors
        """
        self.__id = None

        self.__collection = collection
        self.__spec = spec
        self.__fields = fields
        self.__skip = skip
        self.__limit = limit
        self.__slave_okay = slave_okay
        self.__timeout = timeout
        self.__tailable = tailable
        self.__snapshot = snapshot
        self.__ordering = sort and helpers._index_document(sort) or None
        self.__max_scan = max_scan
        self.__explain = False
        self.__hint = None
        self.__socket = _sock
        self.__must_use_master = _must_use_master
        self.__is_command = _is_command

        self.__data = []
        self.__connection_id = None
        self.__retrieved = 0
        self.__killed = False

    def sort(self, key_or_list, direction=None):
        """Sorts this cursor's results.

        Pass a field name and a direction, either
        :data:`~pymongo.ASCENDING` or :data:`~pymongo.DESCENDING`::

            for doc in collection.find().sort('field', pymongo.ASCENDING):
                print(doc)

        To sort by multiple fields, pass a list of (key, direction) pairs::

            for doc in collection.find().sort([
                    ('field1', pymongo.ASCENDING),
                    ('field2', pymongo.DESCENDING)]):
                print(doc)

        Beginning with MongoDB version 2.6, text search results can be
        sorted by relevance::

            cursor = db.test.find(
                {'$text': {'$search': 'some words'}},
                {'score': {'$meta': 'textScore'}})

            # Sort by 'score' field.
            cursor.sort([('score', {'$meta': 'textScore'})])

            for doc in cursor:
                print(doc)

        Raises :class:`~pymongo.errors.InvalidOperation` if this cursor has
        already been used. Only the last :meth:`sort` applied to this
        cursor has any effect.

        :Parameters:
          - `key_or_list`: a single key or a list of (key, direction)
            pairs specifying the keys to sort on
          - `direction` (optional): only used if `key_or_list` is a single
            key, if not given :data:`~pymongo.ASCENDING` is assumed
        """
        self.__check_okay_to_chain()
        keys = helpers._index_list(key_or_list, direction)
        self.__ordering = helpers._index_document(keys)
        return self

    def __init__(self,collection, 
                 spec, 
                 fields, 
                 skip, 
                 limit, 
                 slave_okay,
                 timeout, 
                 tailable, 
                 snapshot=False,
                 _IOStream=None, 
                 _must_use_master=False, 
                 _is_command=False,
                 as_class=None,
                 sort = None):

        if as_class is None:
            as_class = collection.database.connection.document_class

        self.__collection = collection
        self.__spec = spec
        self.__fields = fields
        self.__skip = skip
        self.__limit = limit
        self.__slave_okay = slave_okay
        self.__timeout = timeout
        self.__tailable = tailable
        self.__snapshot = snapshot
        self.__ordering = sort and helpers._index_document(sort) or None
        self.__explain = False
        self.__hint = None
        self.__IOStream = _IOStream
        self.__must_use_master = _must_use_master
        self.__is_command = _is_command
        self.__as_class = as_class

        self.__data = []
        self.__id = None
        self.__connection_id = None
        self.__retrieved = 0
        self.__killed = False

    def sort(self, key_or_list, direction=None):
        """Sorts this cursor's results.

        Takes either a single key and a direction, or a list of (key,
        direction) pairs. The key(s) must be an instance of ``(str,
        unicode)``, and the direction(s) must be one of
        (:data:`~pymongo.ASCENDING`,
        :data:`~pymongo.DESCENDING`). Raises
        :class:`~pymongo.errors.InvalidOperation` if this cursor has
        already been used. Only the last :meth:`sort` applied to this
        cursor has any effect.

        :Parameters:
          - `key_or_list`: a single key or a list of (key, direction)
            pairs specifying the keys to sort on
          - `direction` (optional): only used if `key_or_list` is a single
            key, if not given :data:`~pymongo.ASCENDING` is assumed
        """
        self.__check_okay_to_chain()
        keys = helpers._index_list(key_or_list, direction)
        self.__ordering = helpers._index_document(keys)
        return self

    def create_index(self, key_or_list, cache_for=300, **kwargs):
        """Creates an index on this collection.

        Takes either a single key or a list of (key, direction) pairs.
        The key(s) must be an instance of :class:`basestring`
        (:class:`str` in python 3), and the directions must be one of
        (:data:`~pymongo.ASCENDING`, :data:`~pymongo.DESCENDING`,
        :data:`~pymongo.GEO2D`). Returns the name of the created index.

        All optional index creation paramaters should be passed as
        keyword arguments to this method. Valid options include:
        check http://docs.mongodb.org/manual/reference/method/db.collection.ensureIndex/#db.collection.ensureIndex
        """
        keys = _index_list(key_or_list)
        index = {"key": _index_document(keys), "ns": self._collection_name}
        name = "name" in kwargs and kwargs["name"] or helpers._gen_index_name(keys)
        index["name"] = name
        index.update(kwargs)

        Client(self._database, 'system.indexes').insert(index, check_keys=False)
        self._database._cache_index(self._collection, name, cache_for)

        return name

    def create_index(self, key_or_list, unique=False, ttl=300):
        """Creates an index on this collection.

        Takes either a single key or a list of (key, direction) pairs.
        The key(s) must be an instance of :class:`basestring`, and the
        directions must be one of (:data:`~pymongo.ASCENDING`,
        :data:`~pymongo.DESCENDING`). Returns the name of the created
        index.

        :Parameters:
          - `key_or_list`: a single key or a list of (key, direction)
            pairs specifying the index to create
          - `unique` (optional): should this index guarantee
            uniqueness?
          - `ttl` (optional): time window (in seconds) during which
            this index will be recognized by subsequent calls to
            :meth:`ensure_index` - see documentation for
            :meth:`ensure_index` for details
        """
        if not isinstance(key_or_list, (str, unicode, list)):
            raise TypeError("key_or_list must either be a single key "
                            "or a list of (key, direction) pairs")

        to_save = SON()
        keys = helpers._index_list(key_or_list)
        name = self._gen_index_name(keys)
        to_save["name"] = name
        to_save["ns"] = self.__full_name
        to_save["key"] = helpers._index_document(keys)
        to_save["unique"] = unique

        self.__database.connection._cache_index(self.__database.name,
                                                self.__name, name, ttl)

        self.__database.system.indexes.insert(to_save, manipulate=False,
                                              check_keys=False)
        return to_save["name"]

    def __init__(self, collection, spec=None, fields=None, skip=0, limit=0,
                 timeout=True, snapshot=False, tailable=False, sort=None,
                 max_scan=None, as_class=None, slave_okay=False,
                 await_data=False, partial=False, manipulate=True,
                 read_preference=ReadPreference.PRIMARY, tag_sets=[{}],
                 secondary_acceptable_latency_ms=None,
                 _must_use_master=False, _uuid_subtype=None, **kwargs):
        """Create a new cursor.

        Should not be called directly by application developers - see
        :meth:`~pymongo.collection.Collection.find` instead.

        .. mongodoc:: cursors
        """
        self.__id = None

        if spec is None:
            spec = {}

        if not isinstance(spec, dict):
            raise TypeError("spec must be an instance of dict")
        if not isinstance(skip, int):
            raise TypeError("skip must be an instance of int")
        if not isinstance(limit, int):
            raise TypeError("limit must be an instance of int")
        if not isinstance(timeout, bool):
            raise TypeError("timeout must be an instance of bool")
        if not isinstance(snapshot, bool):
            raise TypeError("snapshot must be an instance of bool")
        if not isinstance(tailable, bool):
            raise TypeError("tailable must be an instance of bool")
        if not isinstance(slave_okay, bool):
            raise TypeError("slave_okay must be an instance of bool")
        if not isinstance(await_data, bool):
            raise TypeError("await_data must be an instance of bool")
        if not isinstance(partial, bool):
            raise TypeError("partial must be an instance of bool")

        if fields is not None:
            if not fields:
                fields = {"_id": 1}
            if not isinstance(fields, dict):
                fields = helpers._fields_list_to_dict(fields)

        if as_class is None:
            as_class = collection.database.connection.document_class

        self.__collection = collection
        self.__spec = spec
        self.__fields = fields
        self.__skip = skip
        self.__limit = limit
        self.__batch_size = 0

        # This is ugly. People want to be able to do cursor[5:5] and
        # get an empty result set (old behavior was an
        # exception). It's hard to do that right, though, because the
        # server uses limit(0) to mean 'no limit'. So we set __empty
        # in that case and check for it when iterating. We also unset
        # it anytime we change __limit.
        self.__empty = False

        self.__timeout = timeout
        self.__tailable = tailable
        self.__await_data = tailable and await_data
        self.__partial = partial
        self.__snapshot = snapshot
        self.__ordering = sort and helpers._index_document(sort) or None
        self.__max_scan = max_scan
        self.__explain = False
        self.__hint = None
        self.__as_class = as_class
        self.__slave_okay = slave_okay
        self.__manipulate = manipulate
        self.__read_preference = read_preference
        self.__tag_sets = tag_sets
        self.__secondary_acceptable_latency_ms = secondary_acceptable_latency_ms
        self.__tz_aware = collection.database.connection.tz_aware
        self.__must_use_master = _must_use_master
        self.__uuid_subtype = _uuid_subtype or collection.uuid_subtype
        self.__query_flags = 0

        self.__data = deque()
        self.__connection_id = None
        self.__retrieved = 0
        self.__killed = False

        # this is for passing network_timeout through if it's specified
        # need to use kwargs as None is a legit value for network_timeout
        self.__kwargs = kwargs

    def create_index(self, key_or_list, deprecated_unique=None,
                     ttl=300, **kwargs):
        """Creates an index on this collection.

        Takes either a single key or a list of (key, direction) pairs.
        The key(s) must be an instance of :class:`basestring`, and the
        directions must be one of (:data:`~pymongo.ASCENDING`,
        :data:`~pymongo.DESCENDING`, :data:`~pymongo.GEO2D`). Returns
        the name of the created index.

        To create a single key index on the key ``'mike'`` we just use
        a string argument:

        >>> my_collection.create_index("mike")

        For a compound index on ``'mike'`` descending and ``'eliot'``
        ascending we need to use a list of tuples:

        >>> my_collection.create_index([("mike", pymongo.DESCENDING),
        ...                             ("eliot", pymongo.ASCENDING)])

        All optional index creation paramaters should be passed as
        keyword arguments to this method. Valid options include:

          - `name`: custom name to use for this index - if none is
            given, a name will be generated
          - `unique`: should this index guarantee uniqueness?
          - `dropDups` or `drop_dups`: should we drop duplicates
            during index creation when creating a unique index?
          - `min`: minimum value for keys in a :data:`~pymongo.GEO2D`
            index
          - `max`: maximum value for keys in a :data:`~pymongo.GEO2D`
            index

        :Parameters:
          - `key_or_list`: a single key or a list of (key, direction)
            pairs specifying the index to create
          - `deprecated_unique`: DEPRECATED - use `unique` as a kwarg
          - `ttl` (optional): time window (in seconds) during which
            this index will be recognized by subsequent calls to
            :meth:`ensure_index` - see documentation for
            :meth:`ensure_index` for details
          - `**kwargs` (optional): any additional index creation
            options (see the above list) should be passed as keyword
            arguments

        .. versionchanged:: 1.5.1
           Accept kwargs to support all index creation options.

        .. versionadded:: 1.5
           The `name` parameter.

        .. seealso:: :meth:`ensure_index`

        .. mongodoc:: indexes
        """
        keys = helpers._index_list(key_or_list)
        index_doc = helpers._index_document(keys)

        index = {"key": index_doc, "ns": self.__full_name}

        if deprecated_unique is not None:
            warnings.warn("using a positional arg to specify unique is "
                          "deprecated, please use kwargs",
                          DeprecationWarning)
            index["unique"] = deprecated_unique

        name = "name" in kwargs and kwargs["name"] or _gen_index_name(keys)
        index["name"] = name

        if "drop_dups" in kwargs:
            kwargs["dropDups"] = kwargs.pop("drop_dups")

        index.update(kwargs)

        self.__database.connection._cache_index(self.__database.name,
                                                self.__name, name, ttl)

        self.__database.system.indexes.insert(index, manipulate=False,
                                              check_keys=False)
        return name

    def __init__(self, collection, filter=None, projection=None, skip=0,
                 limit=0, no_cursor_timeout=False,
                 cursor_type=CursorType.NON_TAILABLE,
                 sort=None, allow_partial_results=False, oplog_replay=False,
                 modifiers=None, batch_size=0, manipulate=True,
                 collation=None, hint=None, max_scan=None, max_time_ms=None,
                 max=None, min=None, return_key=False, show_record_id=False,
                 snapshot=False, comment=None, session=None):
        """Create a new cursor.

        Should not be called directly by application developers - see
        :meth:`~pymongo.collection.Collection.find` instead.

        .. mongodoc:: cursors
        """
        # Initialize all attributes used in __del__ before possibly raising
        # an error to avoid attribute errors during garbage collection.
        self.__id = None
        self.__exhaust = False
        self.__exhaust_mgr = None
        self.__killed = False

        if session:
            self.__session = session
            self.__explicit_session = True
        else:
            self.__session = None
            self.__explicit_session = False

        spec = filter
        if spec is None:
            spec = {}

        validate_is_mapping("filter", spec)
        if not isinstance(skip, int):
            raise TypeError("skip must be an instance of int")
        if not isinstance(limit, int):
            raise TypeError("limit must be an instance of int")
        validate_boolean("no_cursor_timeout", no_cursor_timeout)
        if cursor_type not in (CursorType.NON_TAILABLE, CursorType.TAILABLE,
                               CursorType.TAILABLE_AWAIT, CursorType.EXHAUST):
            raise ValueError("not a valid value for cursor_type")
        validate_boolean("allow_partial_results", allow_partial_results)
        validate_boolean("oplog_replay", oplog_replay)
        if modifiers is not None:
            warnings.warn("the 'modifiers' parameter is deprecated",
                          DeprecationWarning, stacklevel=2)
            validate_is_mapping("modifiers", modifiers)
        if not isinstance(batch_size, integer_types):
            raise TypeError("batch_size must be an integer")
        if batch_size < 0:
            raise ValueError("batch_size must be >= 0")

        if projection is not None:
            if not projection:
                projection = {"_id": 1}
            projection = helpers._fields_list_to_dict(projection, "projection")

        self.__collection = collection
        self.__spec = spec
        self.__projection = projection
        self.__skip = skip
        self.__limit = limit
        self.__batch_size = batch_size
        self.__modifiers = modifiers and modifiers.copy() or {}
        self.__ordering = sort and helpers._index_document(sort) or None
        self.__max_scan = max_scan
        self.__explain = False
        self.__comment = comment
        self.__max_time_ms = max_time_ms
        self.__max_await_time_ms = None
        self.__max = max
        self.__min = min
        self.__manipulate = manipulate
        self.__collation = validate_collation_or_none(collation)
        self.__return_key = return_key
        self.__show_record_id = show_record_id
        self.__snapshot = snapshot
        self.__set_hint(hint)

        # Exhaust cursor support
        if cursor_type == CursorType.EXHAUST:
            if self.__collection.database.client.is_mongos:
                raise InvalidOperation('Exhaust cursors are '
                                       'not supported by mongos')
            if limit:
                raise InvalidOperation("Can't use limit and exhaust together.")
            self.__exhaust = True

        # This is ugly. People want to be able to do cursor[5:5] and
        # get an empty result set (old behavior was an
        # exception). It's hard to do that right, though, because the
        # server uses limit(0) to mean 'no limit'. So we set __empty
        # in that case and check for it when iterating. We also unset
        # it anytime we change __limit.
        self.__empty = False

        self.__data = deque()
        self.__address = None
        self.__retrieved = 0
#.........这里部分代码省略.........

#.........这里部分代码省略.........
        if not isinstance(spec, dict):
            raise TypeError("spec must be an instance of dict")
        if not isinstance(skip, int):
            raise TypeError("skip must be an instance of int")
        if not isinstance(limit, int):
            raise TypeError("limit must be an instance of int")
        if not isinstance(timeout, bool):
            raise TypeError("timeout must be an instance of bool")
        if not isinstance(snapshot, bool):
            raise TypeError("snapshot must be an instance of bool")
        if not isinstance(tailable, bool):
            raise TypeError("tailable must be an instance of bool")
        if not isinstance(slave_okay, bool):
            raise TypeError("slave_okay must be an instance of bool")
        if not isinstance(await_data, bool):
            raise TypeError("await_data must be an instance of bool")
        if not isinstance(partial, bool):
            raise TypeError("partial must be an instance of bool")
        if not isinstance(exhaust, bool):
            raise TypeError("exhaust must be an instance of bool")
        if not isinstance(oplog_replay, bool):
            raise TypeError("oplog_replay must be an instance of bool")

        if fields is not None:
            if not fields:
                fields = {"_id": 1}
            if not isinstance(fields, dict):
                fields = helpers._fields_list_to_dict(fields)

        self.__collection = collection
        self.__spec = spec
        self.__fields = fields
        self.__skip = skip
        self.__limit = limit
        self.__max_time_ms = None
        self.__batch_size = 0
        self.__max = None
        self.__min = None
        self.__modifiers = modifiers and modifiers.copy() or {}


        # Exhaust cursor support
        if self.__collection.database.connection.is_mongos and exhaust:
            raise InvalidOperation('Exhaust cursors are '
                                   'not supported by mongos')
        if limit and exhaust:
            raise InvalidOperation("Can't use limit and exhaust together.")
        self.__exhaust = exhaust
        self.__exhaust_mgr = None

        # This is ugly. People want to be able to do cursor[5:5] and
        # get an empty result set (old behavior was an
        # exception). It's hard to do that right, though, because the
        # server uses limit(0) to mean 'no limit'. So we set __empty
        # in that case and check for it when iterating. We also unset
        # it anytime we change __limit.
        self.__empty = False

        self.__snapshot = snapshot
        self.__ordering = sort and helpers._index_document(sort) or None
        self.__max_scan = max_scan
        self.__explain = False
        self.__hint = None
        self.__comment = None
        self.__slave_okay = slave_okay
        self.__manipulate = manipulate
        self.__read_preference = read_preference
        self.__tag_sets = tag_sets
        self.__secondary_acceptable_latency_ms = secondary_acceptable_latency_ms
        self.__compile_re = compile_re
        self.__must_use_master = _must_use_master

        copts = _codec_options or collection.codec_options
        if as_class is not None:
            copts = _CodecOptions(
                as_class, copts.tz_aware, copts.uuid_representation)
        self.__codec_options = copts

        self.__data = deque()
        self.__connection_id = None
        self.__retrieved = 0
        self.__killed = False

        self.__query_flags = 0
        if tailable:
            self.__query_flags |= _QUERY_OPTIONS["tailable_cursor"]
        if not timeout:
            self.__query_flags |= _QUERY_OPTIONS["no_timeout"]
        if tailable and await_data:
            self.__query_flags |= _QUERY_OPTIONS["await_data"]
        if exhaust:
            self.__query_flags |= _QUERY_OPTIONS["exhaust"]
        if partial:
            self.__query_flags |= _QUERY_OPTIONS["partial"]
        if oplog_replay:
            self.__query_flags |= _QUERY_OPTIONS["oplog_replay"]

        # this is for passing network_timeout through if it's specified
        # need to use kwargs as None is a legit value for network_timeout
        self.__kwargs = kwargs

    def __init__(self, collection, spec=None, fields=None, skip=0, limit=0,
                 timeout=True, snapshot=False, tailable=False, sort=None,
                 max_scan=None, as_class=None,
                 await_data=False, partial=False, manipulate=True,
                 read_preference=None, exhaust=False, compile_re=True,
                 _uuid_subtype=None):
        """Create a new cursor.

        Should not be called directly by application developers - see
        :meth:`~pymongo.collection.Collection.find` instead.

        .. mongodoc:: cursors
        """
        self.__id = None

        if spec is None:
            spec = {}

        if not isinstance(spec, dict):
            raise TypeError("spec must be an instance of dict")
        if not isinstance(skip, int):
            raise TypeError("skip must be an instance of int")
        if not isinstance(limit, int):
            raise TypeError("limit must be an instance of int")
        if not isinstance(timeout, bool):
            raise TypeError("timeout must be an instance of bool")
        if not isinstance(snapshot, bool):
            raise TypeError("snapshot must be an instance of bool")
        if not isinstance(tailable, bool):
            raise TypeError("tailable must be an instance of bool")
        if not isinstance(await_data, bool):
            raise TypeError("await_data must be an instance of bool")
        if not isinstance(partial, bool):
            raise TypeError("partial must be an instance of bool")
        if not isinstance(exhaust, bool):
            raise TypeError("exhaust must be an instance of bool")

        if fields is not None:
            if not fields:
                fields = {"_id": 1}
            if not isinstance(fields, dict):
                fields = helpers._fields_list_to_dict(fields)

        if as_class is None:
            as_class = collection.database.connection.document_class

        self.__collection = collection
        self.__spec = spec
        self.__fields = fields
        self.__skip = skip
        self.__limit = limit
        self.__max_time_ms = None
        self.__batch_size = 0
        self.__max = None
        self.__min = None

        # Exhaust cursor support
        if self.__collection.database.connection.is_mongos and exhaust:
            raise InvalidOperation('Exhaust cursors are '
                                   'not supported by mongos')
        if limit and exhaust:
            raise InvalidOperation("Can't use limit and exhaust together.")
        self.__exhaust = exhaust
        self.__exhaust_mgr = None

        # This is ugly. People want to be able to do cursor[5:5] and
        # get an empty result set (old behavior was an
        # exception). It's hard to do that right, though, because the
        # server uses limit(0) to mean 'no limit'. So we set __empty
        # in that case and check for it when iterating. We also unset
        # it anytime we change __limit.
        self.__empty = False

        self.__snapshot = snapshot
        self.__ordering = sort and helpers._index_document(sort) or None
        self.__max_scan = max_scan
        self.__explain = False
        self.__hint = None
        self.__comment = None
        self.__as_class = as_class
        self.__manipulate = manipulate
        self.__read_preference = read_preference or collection.read_preference
        self.__tz_aware = collection.database.connection.tz_aware
        self.__compile_re = compile_re
        self.__uuid_subtype = _uuid_subtype or collection.uuid_subtype

        self.__data = deque()
        self.__connection_id = None
        self.__retrieved = 0
        self.__killed = False

        self.__query_flags = 0
        if tailable:
            self.__query_flags |= _QUERY_OPTIONS["tailable_cursor"]
        if self.__read_preference != ReadPreference.PRIMARY:
            self.__query_flags |= _QUERY_OPTIONS["slave_okay"]
        if not timeout:
            self.__query_flags |= _QUERY_OPTIONS["no_timeout"]
        if tailable and await_data:
            self.__query_flags |= _QUERY_OPTIONS["await_data"]
#.........这里部分代码省略.........