public function withNotModified()
    {
        return $this->withStatus(304)
            ->withoutHeader('Allow')
            ->withoutHeader('Content-Encoding')
            ->withoutHeader('Content-Language')
            ->withoutHeader('Content-Length')
            ->withoutHeader('Content-MD5')
            ->withoutHeader('Content-Type')
            ->withoutHeader('Last-Modified')
            ->withBody(new Stream('php://temp'));
    }