code: func (r *ReadGroup) SetName(n string) error {
  	if r.owner != nil {
  		id, exists := r.owner.seenGroups[n]
  		if exists {
  			if id != r.id {
  				return errors.New("sam: name exists")
  			}
  			return nil
  		}
  		delete(r.owner.seenGroups, r.name)
  		r.owner.seenGroups[n] = r.id
  	}
  	r.name = n
  	return nil
  }
docs: // SetName sets the read group's name to n.