protected function request($options = [])
    {
        try {
            $params = array_filter($this->params);
            $response = $this->getClient()
                ->get($this->getUrl(), ['query' => $params], $options);

            return trim($this->format) === 'json'
                ? json_decode($response->getBody(), true)
                : simplexml_load_string($response->getBody());
        } catch (RequestException $e) {
            return null;
        }
    }