code: public function listOrders($request)
      {
          if (!($request instanceof MarketplaceWebServiceOrders_Model_ListOrdersRequest)) {
              $request = new MarketplaceWebServiceOrders_Model_ListOrdersRequest($request);
          }
          $parameters = $request->toQueryParameterArray();
          $parameters['Action'] = 'ListOrders';
          $httpResponse = $this->_invoke($parameters);
  
          $response = MarketplaceWebServiceOrders_Model_ListOrdersResponse::fromXML($httpResponse['ResponseBody']);
          $response->setResponseHeaderMetadata($httpResponse['ResponseHeaderMetadata']);
          return $response;
      }
docs: List Orders
  ListOrders can be used to find orders that meet the specified criteria.
  
  @param mixed $request array of parameters for MarketplaceWebServiceOrders_Model_ListOrders request or MarketplaceWebServiceOrders_Model_ListOrders object itself
  @see MarketplaceWebServiceOrders_Model_ListOrdersRequest
  @return MarketplaceWebServiceOrders_Model_ListOrdersResponse
  
  @throws MarketplaceWebServiceOrders_Exception