def save_to_xml(self, obj, filename, tags, version=None):
        root = self.write_xml_object(obj)
        if version is None:
            version = my_version
        root.set('version', version)
        for k, v in tags.iteritems():
            root.set(k, v)
        tree = ElementTree.ElementTree(root)
        self.write_xml_file(filename, tree)
save_to_xml(obj : object, filename: str, tags: dict,
dataset/ETHPy150Open VisTrails/VisTrails/vistrails/db/versions/v0_9_4/persistence/__init__.py/DAOList.save_to_xml