code: func (cg *Consumergroup) Instances() (ConsumergroupInstanceList, error) {
  	root := fmt.Sprintf("%s/consumers/%s/ids", cg.kz.conf.Chroot, cg.Name)
  	cgis, _, err := cg.kz.conn.Children(root)
  	if err != nil {
  		if err == zk.ErrNoNode {
  			result := make(ConsumergroupInstanceList, 0)
  			return result, nil
  		}
  		return nil, err
  	}
  
  	result := make(ConsumergroupInstanceList, 0, len(cgis))
  	for _, cgi := range cgis {
  		result = append(result, cg.Instance(cgi))
  	}
  	return result, nil
  }
docs: // Instances returns a map of all running instances inside this consumergroup.