def instrument_attribute(self, key, inst, propagated=False):
        if propagated:
            if key not in self.local_attrs:
                return  # don't override local attr with inherited attr
        else:
            self.local_attrs[key] = inst
            self.install_descriptor(key, inst)
        self[key] = inst

        for cls in self.class_.__subclasses__():
            manager = self._subclass_manager(cls)
            manager.instrument_attribute(key, inst, True)
dataset/ETHPy150Open RoseOu/flasky/venv/lib/python2.7/site-packages/sqlalchemy/orm/instrumentation.py/ClassManager.instrument_attribute/operator `in` -> `not in`