function form_handler()
 {
     if (empty($_POST['action']) || !$this->tabs->contains($_POST['action'])) {
         return;
     }
     check_admin_referer($this->nonce);
     if (!empty($_POST['download_system_info'])) {
         $this->download_system_info();
     } else {
         parent::form_handler();
     }
 }