def add_filter(self, filt):
        self.active_filters.append(filt)
        self.cache_reset()
A successful subscription on root node should return no node attribute.
dataset/ETHPy150Open roglew/pappy-proxy/pappyproxy/context.py/Context.add_filter--crossover with--dataset/ETHPy150Open ralphm/wokkel/wokkel/test/test_pubsub.py/PubSubServiceTest.test_on_subscribeEmptyNode