code: func ParseStringSet(s string) (*StringSet, error) {
  	ss := &StringSet{}
  	if s == "" {
  		return nil, errors.New("cannot be empty")
  	}
  
  	*ss = strings.Split(s, ",")
  
  	return ss, nil
  }
docs: // ParseStringSet parses the s to a StringSet.
  // The s shoud be a comma separated string.