code: public function init()
      {
          parent::init();
          $this->initOptions();
          $this->initDefaultButtons();
          
          echo Html::beginTag('div', $this->options) . "\n";
          echo Html::beginTag('div', ['class' => 'box ' . $this->type]) . "\n";
          echo $this->renderHeader() . "\n";
          echo $this->renderBodyBegin() . "\n";
      }
docs: Initializes the widget.