Thanks for the hint. Here's what worked for me:
class Toppings:
...
class META:
admin = meta.Admin(ordering=('_order',))
order_with_respect_to = 'pizza'and now the orderings seem to work. ... but (and there's always a but, huh?) now on an individual topping edit page the pizza is blank (just a plus icon to create a new pizza). I'd created these toppings as part of the create pizza and they show up on the pizza edit page. I must be missing something...
