code: func deleteFromSet(set string, value string) string {
  	sets := strings.Split(set, ",")
  	res := make([]string, 0, len(sets))
  	for _, v := range sets {
  		if v != value {
  			res = append(res, v)
  		}
  	}
  	return strings.Join(res, ",")
  }
docs: // deleteFromSet delete the value from the set, e.g:
  // deleteFromSet("Select,Insert,Update", "Update") returns "Select,Insert".