Comment 2 for bug 529746

I've not been involved in the refactoring so I'll just drop my thoughts:

That certainly fixes it, but I have two questions:
 - I remember Lionel saying "always pass ids as arguments, never objects except when needed". Shouldn't the tid be passed instead?
 - the add_parent declaration in task.py has a comment "Take a tid object as parameter", but it really wants a task object.