brr -- from the description it just sounds like np.argmax... and probably it is -- but with our Dataset's in mind, right?

What about generalizing it -- e.g. making a class allowing any function (like np.argmax) to be given, and then instantiating winner_take_all ? (similar to what we have mean_sample as a factory function for FxMapper)?  I even wonder if it could further be "unified" alongside with FxMapper -- very similar and just differ that here there should be no need to merge attributes values, but then this could benefit from what FxMapper already allows with groupping by any given set of attributes... ?