@staticmethod
    def order_estimated_time_delivery(tables):
        pool = Pool()
        ShippingMode = pool.get('shipping.mode')
        table, _ = tables[None]
        if 'shipping_mode' not in tables:
            shipping_mode = ShippingMode.__table__()
            tables['shipping_mode'] = {
                None: (shipping_mode, table.shipping_mode == shipping_mode.id),
            }
        else:
            shipping_mode = tables['shipping_mode']
        return [Case(
            (table.planned_date == Null, Null),
            else_=Case(
                (table.shipping_mode == Null, table.planned_date),
                else_=(table.planned_date - shipping_mode.lead_time),
            ),
        )]