Hi all 
i need to know what is the error in this code 
%for product, lines in groupby(trip.order_lines, lambda l : l.product_id.name) :
<% qt = int(sum([l.qty for l in lines])) %>
i try to get the sm of all product quantity , but i didn't get it i get product and thier quantity not gruoped 
what can i do 
