public function offsetGet($offset)
    {
        if ($offset === 'headers') {
            $headers = [
                'HTTP/' . $this->getResponse()->getProtocolVersion() . ' ' . $this->getResponse()->getStatusCode() . ' ' . $this->getResponse()->getReasonPhrase()
            ];
            foreach ($this->getResponse()->getHeaders() as $header => $values) {
                foreach ($values as $value) {
                    $headers[] = $header . ': ' . $value;
                }
            }

            return $headers;
        }
    }