def METHOD_NAME(self):
    # Test maintaining downstream notifier
    class ChildObserver(DummyObserver):
        def iter_observables(self, object):
            yield object
    instance = ClassWithSet()
    instance.values = set()
    notifier = DummyNotifier()
    child_observer = ChildObserver(notifier=notifier)
    graph = create_graph(
        create_observer(notify=False, optional=False),
        child_observer,
    )
    handler = mock.Mock()
    call_add_or_remove_notifiers(
        object=instance.values,
        graph=graph,
        handler=handler,
    )
    # when
    observable = DummyObservable()
    instance.values.add(observable)
    # then
    self.assertEqual(observable.notifiers, [notifier])
    # when
    instance.values.remove(observable)
    # then
    self.assertEqual(observable.notifiers, [])