code: public function initOptions()
      {
          Ui::addCssClasses($this->options, ['ui', 'message']);
          if (!empty($this->header) && isset($this->header['options'])) {
              Ui::addCssClass($this->header['options'], 'header');
          }
          if (isset($this->icon)) {
              Ui::addCssClass($this->options, 'icon');
          }
      }
docs: Initializes the widget options