code: public function normalize($item, $format = null, array $context = [])
      {
          $data = [];
  
          if ($this->contextHasGroup('Summary', $context)) {
              $saleItem = $item->getSaleItem();
  
              $data = array_replace($data, [
                  'designation'      => $saleItem->getDesignation(),
                  'reference'        => $saleItem->getReference(),
                  'quantity'         => $item->getQuantity(),
                  'total'            => $saleItem->getTotalQuantity(),
              ]);
          }
  
          return $data;
      }
docs: @inheritdoc
  
  @param ShipmentItemInterface $item