code: func (cgi *ConsumergroupInstance) Registered() (bool, error) {
  	node := fmt.Sprintf("%s/consumers/%s/ids/%s", cgi.cg.kz.conf.Chroot, cgi.cg.Name, cgi.ID)
  	return cgi.cg.kz.exists(node)
  }
docs: // Registered checks whether the consumergroup instance is registered in Zookeeper.