public function setAsNotModified()
    {
        $this->setStatusCode(304)->setContent(null);

        $headersToRemove = [
            'Allow',
            'Content-Encoding',
            'Content-Language',
            'Content-Length',
            'Content-MD5',
            'Content-Type',
            'Last-Modified',
        ];

        foreach ($headersToRemove as $header) {
            //remove header key
            $this->headers->remove($header);
        }

        return $this;
    }