code: private function hasStockableSubject(Common\SaleItemInterface $saleItem)
      {
          if (!$saleItem instanceof Stock\StockAssignmentsInterface) {
              return false;
          }
  
          if (null === $subject = $this->subjectHelper->resolve($saleItem)) {
              return false;
          }
  
          if (!$subject instanceof Stock\StockSubjectInterface) {
              return false;
          }
  
          if ($subject->isStockCompound()) {
              return false;
          }
  
          if ($subject->getStockMode() === Stock\StockSubjectModes::MODE_DISABLED) {
              return false;
          }
  
          return true;
      }
docs: Returns whether or not the sale item has a stockable subject.
  
  @param Common\SaleItemInterface $saleItem
  
  @return bool