def __init__(self, conf, engine=None):
        super(SQLAlchemyBackend, self).__init__(conf)
        if engine is not None:
            self._engine = engine
            self._owns_engine = False
        else:
            self._engine = self._create_engine(self._conf)
            self._owns_engine = True
        self._validated = False
        self._upgrade_lock = threading.Lock()
        try:
            self._max_retries = misc.as_int(self._conf.get('max_retries'))
        except __HOLE__:
            self._max_retries = 0
dataset/ETHPy150Open openstack/taskflow/taskflow/persistence/backends/impl_sqlalchemy.py/SQLAlchemyBackend.__init__