private function convertRequestToken($consumer_key, $request_token)
    {
        $params = array(
            'consumer_key'  => $consumer_key,
            'code'  => $request_token
        );

        $request = $this->getClient()->post('/v3/oauth/authorize');
        $request->getParams()->set('redirect.strict', true);
        $request->setHeader('Content-Type', 'application/json; charset=UTF8');
        $request->setHeader('X-Accept', 'application/json');
        $request->setBody(json_encode($params));
        $response = $request->send();

        $data = json_decode($response->getBody());

        return $data;
    }