backend.Address - All of the Dataclasses us Marshmallow for Serialisation This is the adress. It contains coordinates but also the adress
backend.API - This interacts with the external odoo 13 API with XMLrpc
backend.Sale - Unlike pythons dynamic Typing we use statically Typed Classes This allows us to catch TypeErrors and thus allows us to validate the Answer from the Server
backend.Sale_Line - This class is one line of a sail. The relation Ship is many sale_lines to one sale