from trytond.model import Model, ModelSQL, ModelView, fields class Device(Model): 'Devices' __name__ = 'sale_device' name = fields.Char("Name") ip_address = fields.Char('IP Address or Network', help='IPv4 or IPv6 IP address or network. Valid values include: 192.168.0.26 or 192.168.0.0/24') class Printer(Device, ModelSQL, ModelView): 'Printer' __name__ = 'sale.printer' zone = fields.Selection([('bar', "Bar"), ('kitchen', "Kitchen"), ('reception', "Reception")], "Zone") shop = fields.Many2One('sale.shop', "Shop") api = fields.Many2One('sale.printer_api', "API") class Api(Device, ModelSQL, ModelView): 'Api printer' __name__ = 'sale.printer_api'