code: func ZonesToSet(zonesString string) (sets.String, error) {
  	zones, err := stringToSet(zonesString, ",")
  	if err != nil {
  		return nil, fmt.Errorf("error parsing zones %s, must be strings separated by commas: %v", zonesString, err)
  	}
  	return zones, nil
  }
docs: // ZonesToSet converts a string containing a comma separated list of zones to set