code: func (t ErrorType) String() string {
  	switch t {
  	case ErrorTypeNotFound:
  		return "Not found"
  	case ErrorTypeRequired:
  		return "Required value"
  	case ErrorTypeDuplicate:
  		return "Duplicate value"
  	case ErrorTypeInvalid:
  		return "Invalid value"
  	case ErrorTypeNotSupported:
  		return "Unsupported value"
  	case ErrorTypeForbidden:
  		return "Forbidden"
  	case ErrorTypeTooLong:
  		return "Too long"
  	case ErrorTypeInternal:
  		return "Internal error"
  	default:
  		panic(fmt.Sprintf("unrecognized validation error: %q", string(t)))
  	}
  }
docs: // String converts a ErrorType into its corresponding canonical error message.