on page 151 of the book agile... we have the following code in the
cart.items.each do |item|
li = LineItem.from_cart_item(item)
line_items << li
what kind of variable is line_items? is it a local, class, instance or
other kind of variable?
if it is local how rails saves the contents of this variable when
saves the order in "save_order" method which is place in the file