public function show($type = null, $format = null)
    {
        $messages = $this->getMessagesForRender($type);

        $this->groupForRender = array();

        $output = '';

        foreach ($messages as $message) {
            if (!$message->isFlash()) {
                if (!is_null($format)) {
                    $message->setFormat($format);
                }

                $output .= $message->render();
            }
        }

        return $output;
    }