protected function parseAccessToken($body)
    {
        if (!is_array($body)) {
            $body = json_decode($body, true);
        }

        if (empty($body['access_token'])) {
            throw new AuthorizeFailedException('Authorize Failed: '.json_encode($body, JSON_UNESCAPED_UNICODE), $body);
        }

        return new AccessToken($body);
    }