private function createDataElement(RequestInterface $request, $nonce, $timestamp)
    {
        $data = [];
        if ($request->getMethod() === 'POST') {
            $data[] = rawurlencode($request->getBody()->getContents());
        }
        $data[] = rawurlencode('oauth_consumer_key=' . $this->key);
        $data[] = rawurlencode('oauth_nonce=' . $nonce);
        $data[] = rawurlencode('oauth_signature_method=HMAC-SHA256');
        $data[] = rawurlencode('oauth_timestamp=' . $timestamp);
        $data[] = rawurlencode('oauth_version=1.0');

        return $data;
    }