code: func DuplicateItems(name, in string) *Validation {
  	msg := fmt.Sprintf(uniqueFail, name, in)
  	if in == "" {
  		msg = fmt.Sprintf(uniqueFailNoIn, name)
  	}
  	return &Validation{
  		code:    UniqueFailCode,
  		Name:    name,
  		In:      in,
  		message: msg,
  	}
  }
docs: // DuplicateItems error for when an array contains duplicates