code: func (t *Tree) Add(topic string, value interface{}) {
  	t.mutex.Lock()
  	defer t.mutex.Unlock()
  
  	t.add(value, 0, strings.Split(topic, t.Separator), t.root)
  }
docs: // Add registers the value for the supplied topic. This function will
  // automatically grow the tree. If value already exists for the given topic it
  // will not be added again.