/**
  * Finds the Config model based on its primary key value.
  * If the model is not found, a 404 HTTP exception will be thrown.
  * @param string $model
  * @param string $item
  * @param string $variant
  * @return Config the loaded model
  * @throws NotFoundHttpException if the model cannot be found
  */
 protected function findModel($model, $item, $variant)
 {
     if (($model = Config::findOne(['model' => $model, 'item' => $item, 'variant' => $variant])) !== null) {
         return $model;
     } else {
         throw new NotFoundHttpException('The requested page does not exist.');
     }
 }