code: public function normalize($order, $format = null, array $context = [])
      {
          $data = parent::normalize($order, $format, $context);
  
          if ($this->contextHasGroup('Summary', $context)) {
              $items = [];
              foreach ($order->getItems() as $item) {
                  $items[] = $this->normalizeObject($item, $format, $context);
              }
  
              $data = array_replace($data, [
                  'items'       => $items,
                  'description' => $order->getDescription(),
              ]);
          }
  
          return $data;
      }
docs: @inheritdoc
  
  @param SupplierOrderInterface $order