protected function performRequest(string $uri)
    {
        $httpResponse = $this->client->get($uri);
        Assert::eq($httpResponse->getStatusCode(), 200, 'Request failed.');

        $content = $httpResponse->getBody()->getContents();
        $xml = simplexml_load_string($content);

        $this->exceptionOnError($xml);

        return $this->responseFactory->getResponse($xml);
    }