public function withNotModified()
    {
        $new = $this->withStatus(304);
        $new->_createStream();
        $remove = [
            'Allow',
            'Content-Encoding',
            'Content-Language',
            'Content-Length',
            'Content-MD5',
            'Content-Type',
            'Last-Modified'
        ];
        foreach ($remove as $header) {
            $new = $new->withoutHeader($header);
        }

        return $new;
    }