def open_from_xml(self, filename, vtType, tree=None):
        """open_from_xml(filename) -> DBVistrail"""
        if tree in None:
            tree = self.parse_xml_file(filename)
        vistrail = self.read_xml_object(vtType, tree.getroot())
        return vistrail
dataset/ETHPy150Open VisTrails/VisTrails/vistrails/db/versions/v0_9_4/persistence/__init__.py/DAOList.open_from_xml/operator `is` -> `in`