yii\bootstrap\Nav::run PHP Method

    public function run()
    {
        BootstrapAsset::register($this->getView());
        return $this->renderItems();
    }

 /**
  * @inheritdoc
  */
 public function run()
 {
     if ($this->direction == 'left') {
         $this->options['class'] .= ' drop-left';
     }
     $itemTree = $this->generateItemsTree($this->items);
     $this->items = $this->createItems($itemTree);
     return parent::run();
 }