These are real failures by the bots. Magmas implements a generic one() by return self(1). Perhaps we should try that first (or more generally

def one(self):
    try:
        return super().one()
    except (TypeError,, ValueError, AttributeError):
        pass
    it = (v for v in self if all(v * w == w for w in self))
    return next(it)

I think there is an implicit general problem as the default iteration starts from one() and multiplies by all of the generators. Of course, this is not unreasonable as we expect the user to implement one of these as part of the monoid. That being said, perhaps it is better to require one be implemented in some more explicit way?

For both methods, perhaps we should cache that result? Also, wouldn't it be better raise a different error than StopIteration if it is not invertible?

That's very curious and unexpected. Now I wonder how that code is even working. It would need some non-generic way to create things (either an iterator or be able to construct one() somehow). I figured the super() call was sufficient, but I guess we should in principle, check that the one from Magmas.Unital is being called (or we could just explicitly add it in as return self(1) instead).

Well, I guess we can just revert like this, but at least it didn't seem like a widespread problem... How much time do you want to spend on this?

Thank you. LGTM.