public function call($method = 'GET', $uri = null, $headers = null, $body = null, array $options = array(), $classToUnserialize = null)
    {
        $request = $this->client->createRequest($method, $uri, $headers, $body, $options);

        if ($classToUnserialize) {
            return $this->serializer->deserialize(
                (string) $this->send($request)->getBody(),
                $classToUnserialize,
                'xml'
            );
        }

        return $this->send($request);
    }