code: public function normalize($assignment, $format = null, array $context = [])
      {
          $data = [];
  
          if ($this->contextHasGroup(['StockView', 'StockAssignment'], $context)) {
              $formatter = $this->getFormatter();
  
              $data = array_replace($data, [
                  'sold'    => $formatter->number($assignment->getSoldQuantity()),
                  'shipped' => $formatter->number($assignment->getShippedQuantity()),
              ]);
  
              if ($this->contextHasGroup('StockView', $context)) {
                  $sale = $assignment->getSaleItem()->getSale();
                  $data['order_id'] = $sale->getId();
                  $data['preparation'] =
                      $sale instanceof ShipmentSubjectInterface &&
                      $sale->getShipmentState() === ShipmentStates::STATE_PREPARATION;
              }
  
              if ($this->contextHasGroup('StockAssignment', $context)) {
                  $data['unit'] = $this->normalizeObject($assignment->getStockUnit(), $format, $context);
              }
          }
  
          return $data;
      }
docs: @inheritdoc
  
  @param StockAssignmentInterface $assignment