code: protected function initOptions()
      {
          Html::addCssClass($this->options, 'alert');
          
          if($this->fadeeffect){
              Html::addCssClass($this->options, 'fade');
              Html::addCssClass($this->options, 'in');            
          }
          $this->options = array_merge($this->options,['role'=>'alert']);
  
          if ($this->closeButton !== null) {
              $this->closeButton = array_merge([
                  'data-dismiss' => 'alert',
                  'aria-hidden' => 'true',
                  'class' => 'close',
              ], $this->closeButton);
          }
      }
docs: Initializes the widget options.
  This method sets the default values for various options.