code: 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));
      }
docs: Requests an access token from Facebook
  according to the returned code.
  
  @param string $code The code returned from Facebook after authentication
  
  @return Vinelab\Contracts\AccessTokenInterface