Method expunge

lib/sqlalchemy/orm/session.py:3407–3426

Remove the `instance` from this ``Session``. This will free all internal references to the instance. Cascading will be applied according to the *expunge* cascade rule.

(self, instance: object)

            state._detach(self)

    def expunge(self, instance: object) -> None:
        """Remove the `instance` from this ``Session``.

        This will free all internal references to the instance.  Cascading
        will be applied according to the *expunge* cascade rule.

        """
        try:
            state = attributes.instance_state(instance)
        except exc.NO_STATE as err:
            raise exc.UnmappedInstanceError(instance) from err
        if state.session_id is not self.hash_key:
            raise sa_exc.InvalidRequestError(
                "Instance %s is not present in this Session" % state_str(state)
            )

        cascaded = list(
            state.manager.mapper.cascade_iterator("expunge", state)
        )
        self._expunge_states([state] + [st_ for o, m, st_, dct_ in cascaded])

    def _expunge_states(
        self, states: Iterable[InstanceState[Any]], to_transient: bool = False