I am trying to add a delivery date field to the sales order line with a custom module

[quote]

from odoo import models, fields, api

class SaleOrderLine(models.Model):

    _inherit = 'sale.order.line'

    delivery_date = fields.Date(

        string="Delivery Date",

        help="Delivery date for this order line",

        store=True

    )

...

[/quote]

even though the module installs, the additional field is not created in the model sale.order.line

this is on V18 on a fresh db with only the sale module installed; what am I missing?