code: func (b *Bslack) handleTopicOrPurpose(msg *config.Message, channelInfo *slack.Channel) (bool, error) {
  	if msg.Event != config.EventTopicChange {
  		return false, nil
  	}
  
  	if b.GetBool("SyncTopic") {
  		return true, b.updateTopicOrPurpose(msg, channelInfo)
  	}
  
  	// Pass along to normal message handlers.
  	if b.GetBool("ShowTopicChange") {
  		return false, nil
  	}
  
  	// Swallow message as handled no-op.
  	return true, nil
  }
docs: // handles updating topic/purpose and determining whether to further propagate update messages.