When I try to access line item from sales order (from list of orders) as follows:

<for each="order in objects"> <for each="order_line in order"> <order_line.product_id.default_code> </for> </for>

I get this error:

Iteration is not allowed on browse_record(sale.order, 1809) Iteration is not allowed on browse_record(sale.order, 1809)

Any idea ?