def _query_children_for_cache_children(self, course_key, items):
        # first get non-draft in a round-trip
        to_process_non_drafts = super(DraftModuleStore, self)._query_children_for_cache_children(course_key, items)

        to_process_dict = {}
        for non_draft in to_process_non_drafts:
            to_process_dict[Location._from_deprecated_son(non_draft["_id"], course_key.run)] = non_draft

        if self.branch_setting_func() == ModuleStoreEnum.Branch.draft_preferred:
            # now query all draft content in another round-trip
            query = []
            for item in items:
                item_usage_key = course_key.make_usage_key_from_deprecated_string(item)
                if item_usage_key.category not in DIRECT_ONLY_CATEGORIES:
                    query.append(as_draft(item_usage_key).to_deprecated_son())
            if query:
                query = {'_id': {'$in': query}}
                to_process_drafts = list(self.collection.find(query))

                # now we have to go through all drafts and replace the non-draft
                # with the draft. This is because the semantics of the DraftStore is to
                # always return the draft - if available
                for draft in to_process_drafts:
                    draft_loc = Location._from_deprecated_son(draft["_id"], course_key.run)
                    draft_as_non_draft_loc = as_published(draft_loc)

                    # does non-draft exist in the collection
                    # if so, replace it
                    if draft_as_non_draft_loc in to_process_dict:
                        to_process_dict[draft_as_non_draft_loc] = draft

        # convert the dict - which is used for look ups - back into a list
        queried_children = to_process_dict.values()

        return queried_children

 def has_published_version(self, xblock):
     """
     Returns True if this xblock has an existing published version regardless of whether the
     published version is up to date.
     """
     if getattr(xblock, 'is_draft', False):
         published_xblock_location = as_published(xblock.location)
         try:
             xblock.runtime.lookup_item(published_xblock_location)
         except ItemNotFoundError:
             return False
     return True

    def compute_publish_state(self, xblock):
        """
        Returns whether this xblock is draft, public, or private.

        Returns:
            PublishState.draft - content is in the process of being edited, but still has a previous
                version deployed to LMS
            PublishState.public - content is locked and deployed to LMS
            PublishState.private - content is editable and not deployed to LMS
        """
        if getattr(xblock, 'is_draft', False):
            published_xblock_location = as_published(xblock.location)
            try:
                xblock.runtime.lookup_item(published_xblock_location)
            except ItemNotFoundError:
                return PublishState.private
            return PublishState.draft
        else:
            return PublishState.public

    def publish(self, location, user_id):
        """
        Publish the subtree rooted at location to the live course and remove the drafts.
        Such publishing may cause the deletion of previously published but subsequently deleted
        child trees. Overwrites any existing published xblocks from the subtree.

        Treats the publishing of non-draftable items as merely a subtree selection from
        which to descend.

        Raises:
            ItemNotFoundError: if any of the draft subtree nodes aren't found
        """
        # NOTE: cannot easily use self._breadth_first b/c need to get pub'd and draft as pairs
        # (could do it by having 2 breadth first scans, the first to just get all published children
        # and the second to do the publishing on the drafts looking for the published in the cached
        # list of published ones.)
        to_be_deleted = []

        def _internal_depth_first(item_location, is_root):
            """
            Depth first publishing from the given location
            """
            item = self.get_item(item_location)

            # publish the children first
            if item.has_children:
                for child_loc in item.children:
                    _internal_depth_first(child_loc, False)

            if item_location.category in DIRECT_ONLY_CATEGORIES or not getattr(item, 'is_draft', False):
                # ignore noop attempt to publish something that can't be or isn't currently draft
                return

            # try to find the originally PUBLISHED version, if it exists
            try:
                original_published = super(DraftModuleStore, self).get_item(item_location)
            except ItemNotFoundError:
                original_published = None

            # if the category of this item allows having children
            if item.has_children:
                if original_published is not None:
                    # see if previously published children were deleted. 2 reasons for children lists to differ:
                    #   Case 1: child deleted
                    #   Case 2: child moved
                    for orig_child in original_published.children:
                        if orig_child not in item.children:
                            published_parent = self.get_parent_location(orig_child)
                            if published_parent == item_location:
                                # Case 1: child was deleted in draft parent item
                                # So, delete published version of the child now that we're publishing the draft parent
                                self._delete_subtree(orig_child, [as_published])
                            else:
                                # Case 2: child was moved to a new draft parent item
                                # So, do not delete the child.  It will be published when the new parent is published.
                                pass

            super(DraftModuleStore, self).update_item(item, user_id, isPublish=True, is_publish_root=is_root)
            to_be_deleted.append(as_draft(item_location).to_deprecated_son())

        # verify input conditions
        self._verify_branch_setting(ModuleStoreEnum.Branch.draft_preferred)
        _verify_revision_is_published(location)

        _internal_depth_first(location, True)
        if len(to_be_deleted) > 0:
            self.collection.remove({'_id': {'$in': to_be_deleted}})
        return self.get_item(as_published(location))

    def publish(self, location, user_id, **kwargs):
        """
        Publish the subtree rooted at location to the live course and remove the drafts.
        Such publishing may cause the deletion of previously published but subsequently deleted
        child trees. Overwrites any existing published xblocks from the subtree.

        Treats the publishing of non-draftable items as merely a subtree selection from
        which to descend.

        Raises:
            ItemNotFoundError: if any of the draft subtree nodes aren't found

        Returns:
            The newly published xblock
        """
        # NOTE: cannot easily use self._breadth_first b/c need to get pub'd and draft as pairs
        # (could do it by having 2 breadth first scans, the first to just get all published children
        # and the second to do the publishing on the drafts looking for the published in the cached
        # list of published ones.)
        to_be_deleted = []

        def _internal_depth_first(item_location, is_root):
            """
            Depth first publishing from the given location
            """
            try:
                # handle child does not exist w/o killing publish
                item = self.get_item(item_location)
            except ItemNotFoundError:
                log.warning('Cannot find: %s', item_location)
                return

            # publish the children first
            if item.has_children:
                for child_loc in item.children:
                    _internal_depth_first(child_loc, False)

            if item_location.category in DIRECT_ONLY_CATEGORIES or not getattr(item, 'is_draft', False):
                # ignore noop attempt to publish something that can't be or isn't currently draft
                return

            # try to find the originally PUBLISHED version, if it exists
            try:
                original_published = super(DraftModuleStore, self).get_item(item_location)
            except ItemNotFoundError:
                original_published = None

            # if the category of this item allows having children
            if item.has_children:
                if original_published is not None:
                    # see if previously published children were deleted. 2 reasons for children lists to differ:
                    #   Case 1: child deleted
                    #   Case 2: child moved
                    for orig_child in original_published.children:
                        if orig_child not in item.children:
                            published_parent = self.get_parent_location(orig_child)
                            if published_parent == item_location:
                                # Case 1: child was deleted in draft parent item
                                # So, delete published version of the child now that we're publishing the draft parent
                                self._delete_subtree(orig_child, [as_published])
                            else:
                                # Case 2: child was moved to a new draft parent item
                                # So, do not delete the child.  It will be published when the new parent is published.
                                pass

            # update the published (not draft) item (ignoring that item is "draft"). The published
            # may not exist; (if original_published is None); so, allow_not_found
            super(DraftModuleStore, self).update_item(
                item, user_id, isPublish=True, is_publish_root=is_root, allow_not_found=True
            )
            to_be_deleted.append(as_draft(item_location).to_deprecated_son())

        # verify input conditions
        self._verify_branch_setting(ModuleStoreEnum.Branch.draft_preferred)
        _verify_revision_is_published(location)

        _internal_depth_first(location, True)
        course_key = location.course_key
        bulk_record = self._get_bulk_ops_record(course_key)
        if len(to_be_deleted) > 0:
            bulk_record.dirty = True
            self.collection.remove({'_id': {'$in': to_be_deleted}})

        if self.signal_handler and not bulk_record.active:
            self.signal_handler.send("course_published", course_key=course_key)

        # Now it's been published, add the object to the courseware search index so that it appears in search results
        CoursewareSearchIndexer.do_publish_index(self, location)

        return self.get_item(as_published(location))