(self)
return None
If this returns None then the unit unit_description, unit_cost, and quantity
        will not show up for the line item in the printed invoice.
If this returns None then the unit unit_description, unit_cost, and quantity
        will not show up for the line item in the printed invoice.
If this returns None then the unit unit_description unit_cost and quantity will not show up for the line item in the printed invoice .
def unit_description(self):
        """
        If this returns None then the unit unit_description, unit_cost, and quantity
        will not show up for the line item in the printed invoice.
        """
        return None
def unit_description ( self ) : return None