code: public function listFinancialEventGroupsByNextToken($request)
      {
          if (!($request instanceof MWSFinancesService_Model_ListFinancialEventGroupsByNextTokenRequest)) {
              require_once (dirname(__FILE__) . '/Model/ListFinancialEventGroupsByNextTokenRequest.php');
              $request = new MWSFinancesService_Model_ListFinancialEventGroupsByNextTokenRequest($request);
          }
          $parameters = $request->toQueryParameterArray();
          $parameters['Action'] = 'ListFinancialEventGroupsByNextToken';
          $httpResponse = $this->_invoke($parameters);
  
          require_once (dirname(__FILE__) . '/Model/ListFinancialEventGroupsByNextTokenResponse.php');
          $response = MWSFinancesService_Model_ListFinancialEventGroupsByNextTokenResponse::fromXML($httpResponse['ResponseBody']);
          $response->setResponseHeaderMetadata($httpResponse['ResponseHeaderMetadata']);
          return $response;
      }
docs: List Financial Event Groups By Next Token
  If ListFinancialEventGroups returns a nextToken, thus indicating that there are more groups
  than returned that matched the given filter criteria, ListFinancialEventGroupsByNextToken
  can be used to retrieve those groups using that nextToken.
  
  @param mixed $request array of parameters for MWSFinancesService_Model_ListFinancialEventGroupsByNextToken request or MWSFinancesService_Model_ListFinancialEventGroupsByNextToken object itself
  @see MWSFinancesService_Model_ListFinancialEventGroupsByNextTokenRequest
  @return MWSFinancesService_Model_ListFinancialEventGroupsByNextTokenResponse
  
  @throws MWSFinancesService_Exception