Method _cb

Lib/weakref.py:53–60

(arg)

            raise TypeError("argument should be a bound method, not {}"
                            .format(type(meth))) from None
        def _cb(arg):
            # The self-weakref trick is needed to avoid creating a reference
            # cycle.
            self = self_wr()
            if self._alive:
                self._alive = False
                if callback is not None:
                    callback(self)
        self = ref.__new__(cls, obj, _cb)
        self._func_ref = ref(func, _cb)
        self._meth_type = type(meth)