private function _checkRelationExists(Model $model, string $relationName)
    {
        if (!method_exists($model, $relationName) || !$model->{$relationName}() instanceof Relation) {
            if (Lang::has('resource-controller.data2relationinexistent')) {
                $message = trans('resource-controller.data2relationinexistent', ['relationName' => $relationName]);
            } else {
                $message = "Array type request data '{$relationName}' must be named after an existent relation.";
            }

            throw new MassAssignmentException($message);
        }
    }