In any case, if that doesn't work:

> I guess checking for `weak` even if if there are false negatives and providing a hook for subclasses is still good enough to be useful for clients but it does take away from the point of this PR. Are you still for keeping it?

Ehhh… I'd rather have consistent behavior, which would mean not distinguishing transitory and permanent properties automatically. I still like the property behaviors themselves, though, and want to retain the API.