GraphQL\Validator\Rules\UniqueInputFieldNames::duplicateInputFieldMessage PHP Метод

    static function duplicateInputFieldMessage($fieldName)
    {
        return "There can be only one input field named \"{$fieldName}\".";
    }

 private function duplicateField($name, $l1, $c1, $l2, $c2)
 {
     return FormattedError::create(UniqueInputFieldNames::duplicateInputFieldMessage($name), [new SourceLocation($l1, $c1), new SourceLocation($l2, $c2)]);
 }