state.py 文件源码

def _cleanup(self, ref):
        """Weakref callback cleanup.

        This callable cleans out the state when it is being garbage
        collected.

        this _cleanup **assumes** that there are no strong refs to us!
        Will not work otherwise!

        """
        instance_dict = self._instance_dict()
        if instance_dict is not None:
            instance_dict._fast_discard(self)
            del self._instance_dict

            # we can't possibly be in instance_dict._modified
            # b.c. this is weakref cleanup only, that set
            # is strong referencing!
            # assert self not in instance_dict._modified

        self.session_id = self._strong_obj = None
        del self.obj