code: def item_count(self, request, variant_id=None):
          
          bid = utils.basket_id(request)
          item = ProductVariant.objects.get(id=variant_id)
          try:
              count = BasketItem.objects.get(basket_id=bid, variant=item).quantity
          except BasketItem.DoesNotExist:
              count = 0
          return Response(data={"quantity": count}, status=status.HTTP_200_OK)
docs: Get quantity of a single item in the basket