public function requestAccessToken($code)
    {
        if (!$code || empty($code)) {
            throw new InvalidFacebookCodeException();
        }

        $request = [
            'url' => $this->settings['token_url'],

            'params' => [
                'client_id' => $this->settings['api_key'],
                'redirect_uri' => $this->settings['redirect_uri'],
                'client_secret' => $this->settings['secret'],
                'code' => $code,
                'format' => 'json',
            ],
        ];

        return $this->access_token->make($this->http->get($request));
    }