public function actionIndex($parent_id = 1)
 {
     $searchModel = new Navigation(['scenario' => 'search']);
     $searchModel->parent_id = $parent_id;
     $dataProvider = $searchModel->search($_GET);
     $model = null;
     if ($parent_id > 0) {
         $model = Navigation::findOne($parent_id);
     }
     return $this->render('index', ['dataProvider' => $dataProvider, 'searchModel' => $searchModel, 'model' => $model]);
 }