public static function validateMethod($method)
    {
        if ($method === self::METHOD_POST ||
            $method === self::METHOD_PUT ||
            $method === self::METHOD_DELETE ||
            $method === self::METHOD_GET ||
            $method === self::METHOD_HEAD ||
            $method === self::METHOD_PATCH
        ) {
            return true;
        }

        throw new ClientException('Invalid request method \'' . $method . '\'');
    }