'Returns True if the item a discount coupon has been applied to the OrderItem and False otherwise.
Earlier, the OrderItems were stored with an empty list_price if a discount had not been applied.
Now we consider the item to be non discounted if list_price is None or list_price == unit_cost. In
these lines, an item is discounted if it\'s non-None and list_price and unit_cost mismatch.
This should work with both new and old records.'

@property
def is_discounted(self):

    return (self.list_price and (self.list_price != self.unit_cost))
