> I get the following results for builtin objects that have defined subclasses

From that list, the only unhelpful ones with > 4 items, in my opinion, appear to be `object`, since that just tells you every type that exists, and `tuple`, because that lists every single namedtuple.

> So it is USEFUL to know ALL subclasses of a given Exception class

I agree with this - most of the value here comes from showing the full set of exceptions. If we don't do that, we should probably point the user to calling `cls.__subclasses__()` so they can inspect the full list