private function _validate($token)
    {

        $request = $this->_httpClient->createRequest('POST', $this->_tokenServiceUrl . 'validate');
        $postBody = $request->getBody();


        // $postBody is an instance of GuzzleHttp\Post\PostBodyInterface
        $postBody->setField('service', $this->_appID);
        $postBody->setField('token', $token);

        // Send the POST request
        try {
            $response = $this->_httpClient->send($request);
        } catch (ClientException $e) {
            return "BAD_TOKEN";
        } catch (ServerException $e) {
            return "SERVER_ERROR";
        }

        return $response->json();

    }