Added a method for checking tag name conflicts

                self._parent.add_sub_object(sub_id, db.itervalues(),

                                            self._object_types[sub_id])

    def check_tags_conflict(self, *tag_names):

        """Checks a list of tag names that might conflict before inserting in

        TagDB hierarchy

        .. warning::

            This is in no way a guarantee that following inserts will succeed.

        """

        conflicts = []

        parent_check = []

        for name in tag_names:

            if name in self.db['__main__']:

                conflicts.append(name)

            else:

                parent_check.append(name)

        if self._parent is not None and parent_check:

            conflicts.extend(self._parent.check_tags_conflict(*parent_check))

        return conflicts

    # tag handling part, used by plugins

    def add_tags(self, tags, ignore_errors=False):

        """