I've encountered a slightly annoying situation when I
wanted to use the following:

<td tal:content="structure
python:context.product.menu(sort_on='title')"></td>

Where product is a normal Class.

There are two problems with the above:

1. The docstring for
roundup.cgi.templating.LinkHTMLProperty.menu is
inaccurate. The sort_on is just a plain property
string, it'll use a '+' sort no matter what you do,
whereas the docstring says you can use ('+',
'attribute'). So I couldn't do a descending sort.

2. If there is an order attribute present, it ignores
your specified sort and sorts on order. This was a
problem with my product class as it had a left over
order attribute from a previous life. Regardless, there
might be cases where you don't want to sort by order.