code: def getDiscountAmount(self):
          
          has_client_discount = self.aq_parent.getMemberDiscountApplies()
          if has_client_discount:
              discount = Decimal(self.getDefaultMemberDiscount())
              return Decimal(self.getSubtotal() * discount / 100)
          else:
              return 0
docs: It computes and returns the analysis service's discount amount
          without VAT