def uninstall_member(self, key):
        original = self.originals.pop(key, None)
        if original is None:
            setattr(self.class_, key, original)
dataset/ETHPy150Open RoseOu/flasky/venv/lib/python2.7/site-packages/sqlalchemy/orm/instrumentation.py/ClassManager.uninstall_member/operator `is not` -> `is`