code: public function shopRates($rateRequest)
      {
          if ($rateRequest instanceof Shipment) {
              $shipment = $rateRequest;
              $rateRequest = new RateRequest();
              $rateRequest->setShipment($shipment);
          }
  
          $this->requestOption = 'Shop';
  
          return $this->sendRequest($rateRequest);
      }
docs: @param $rateRequest
  
  @throws Exception
  
  @return RateResponse