private function getUserAgent()
    {
        $curlinfo = curl_version();
        $uagent = array();
        $uagent[] = 'gocardless-pro-php/3.0.0';
        $uagent[] = 'schema-version/2015-07-06';
        $uagent[] = 'GuzzleHttp/' . \GuzzleHttp\Client::VERSION;
        $uagent[] = 'php/' . phpversion();
        if (extension_loaded('curl') && function_exists('curl_version')) {
            $uagent[] = 'curl/' . \curl_version()['version'];
            $uagent[] = 'curl/' . \curl_version()['host'];
        }
        return implode(' ', $uagent);
    }