protected function _format($type, $message) {
		$key = 'X-Wf-1-1-1-' . $this->_counter++;

		$content = [['Type' => $this->_levels[$type]], $message];
		$content = json_encode($content);
		$content = strlen($content) . '|' . $content . '|';

		return compact('key', 'content');
	}