code: func stringToSet(str, delimiter string) (sets.String, error) {
  	zonesSlice := strings.Split(str, delimiter)
  	zonesSet := make(sets.String)
  	for _, zone := range zonesSlice {
  		trimmedZone := strings.TrimSpace(zone)
  		if trimmedZone == "" {
  			return make(sets.String), fmt.Errorf(
  				"%q separated list (%q) must not contain an empty string",
  				delimiter,
  				str)
  		}
  		zonesSet.Insert(trimmedZone)
  	}
  	return zonesSet, nil
  }
docs: // StringToSet converts a string containing list separated by specified delimiter to a set