code: func (s *ticketStore) addTopic(topic Topic, register bool) {
  	log.Trace("Adding discovery topic", "topic", topic, "register", register)
  	if s.radius[topic] == nil {
  		s.radius[topic] = newTopicRadius(topic)
  	}
  	if register && s.tickets[topic] == nil {
  		s.tickets[topic] = &topicTickets{buckets: make(map[timeBucket][]ticketRef)}
  	}
  }
docs: // addTopic starts tracking a topic. If register is true,
  // the local node will register the topic and tickets will be collected.