How to use the djangochannelsrestframework.observer.generics.ObserverModelInstanceMixin function in djangochannelsrestframework

async def test_unsubscribe_observer_model_instance_mixin(settings):
    settings.CHANNEL_LAYERS={
        "default": {
            "BACKEND": "channels.layers.InMemoryChannelLayer",
            "TEST_CONFIG": {
                "expiry": 100500,
            },
        },
    }

    layer = channel_layers.make_test_backend(DEFAULT_CHANNEL_LAYER)

    class TestConsumer(ObserverModelInstanceMixin, GenericAsyncAPIConsumer):

        queryset = get_user_model().objects.all()
        serializer_class = UserSerializer

        async def accept(self, subprotocol=None):
            await super().accept()

        @action()
        async def update_username(self, pk=None, username=None, **kwargs):
            user = await database_sync_to_async(self.get_object)(pk=pk)
            user.username = username
            await database_sync_to_async(user.save)()
            return {'pk': pk}, 200

    assert not await database_sync_to_async(get_user_model().objects.all().exists)()

async def test_two_observer_model_instance_mixins(settings):
    settings.CHANNEL_LAYERS={
        "default": {
            "BACKEND": "channels.layers.InMemoryChannelLayer",
            "TEST_CONFIG": {
                "expiry": 100500,
            },
        },
    }

    layer = channel_layers.make_test_backend(DEFAULT_CHANNEL_LAYER)

    class TestUserConsumer(ObserverModelInstanceMixin, GenericAsyncAPIConsumer):

        queryset = get_user_model().objects.all()
        serializer_class = UserSerializer

        async def accept(self, subprotocol=None):
            await super().accept()

        @action()
        async def update_username(self, pk=None, username=None, **kwargs):
            user = await database_sync_to_async(self.get_object)(pk=pk)
            user.username = username
            await database_sync_to_async(user.save)()
            return {'pk': pk}, 200

    class TestOtherConsumer(ObserverModelInstanceMixin, GenericAsyncAPIConsumer):

class TestUserConsumer(ObserverModelInstanceMixin, GenericAsyncAPIConsumer):

        queryset = get_user_model().objects.all()
        serializer_class = UserSerializer

        async def accept(self, subprotocol=None):
            await super().accept()

        @action()
        async def update_username(self, pk=None, username=None, **kwargs):
            user = await database_sync_to_async(self.get_object)(pk=pk)
            user.username = username
            await database_sync_to_async(user.save)()
            return {'pk': pk}, 200

    class TestOtherConsumer(ObserverModelInstanceMixin, GenericAsyncAPIConsumer):

        queryset = TestModel.objects.all()
        serializer_class = UserSerializer

        async def accept(self, subprotocol=None):
            await super().accept()

        @action()
        async def update_username(self, pk=None, name=None, **kwargs):
            tm = await database_sync_to_async(self.get_object)(pk=pk)
            tm.name = name
            await database_sync_to_async(tm.save)()
            return {'pk': pk}, 200

    assert not await database_sync_to_async(
        get_user_model().objects.all().exists)()