Per the discussion in https://trac.sagemath.org/ticket/24757, it would also be nice if some other common iterables like map and filter implemented a similar __length_hint__ which would interrogate whatever iterables were give as their argument(s).

To summarize the discussion in that ticket, it would be nice to at least know if I can expect some iterable to be finite without actually knowing its length.  Sure, if I passed in some arbitrary generator there's no way for the intepreter to know a priori if it will terminate.  But I would at least like to be able to manually mark whether I expect, as an intelligent developer, that under normal conditions the generator *should* terminate.  And this information should filter up to other iterators that I pass my generator to.  That way I can code defensively around whether or not I at least expect an iterator to be finite (even if not of a known length).