def METHOD_NAME(self):
    """
    Flush the list of callbacks with those who are weakly-referencing deleted objects.
    Note: must interact with the self._callbacks directly, and not
    self.callbacks, to avoid infinite recursion.
    """
    _callbacks = []
    for func, arg in self._callbacks:
        if arg is not None:
            arg_ref = arg()
            if arg_ref is None:
                continue
        _callbacks.append((func, arg))
    self._callbacks = _callbacks