private function buildQuery(string $url, string $apiKey, string $locale = null, string $region = null) : string
    {
        if (null !== $apiKey) {
            $url = sprintf('%s&key=%s', $url, $apiKey);
        }
        if (null !== $locale) {
            $url = sprintf('%s&language=%s', $url, $locale);
        }
        if (null !== $region) {
            $url = sprintf('%s&region=%s', $url, $region);
        }

        return $url;
    }