code: func (fs *Filters) removeFromTopicMatchers(watcher *Filter) {
  	delete(fs.allTopicsMatcher, watcher)
  	for _, topic := range watcher.Topics {
  		delete(fs.topicMatcher[BytesToTopic(topic)], watcher)
  	}
  }
docs: // removeFromTopicMatchers removes a filter from the topic matchers