[clusmore]

I had heard of the support for the hierarchy of some builtins like floats being more general than ints, but this isn't a very satisfactory approach because it's not extensible to user-defined numeric types. Perhaps what I'm suggesting is possible with either the existing classes in abc, or by defining more like them (and ensuring users can define their own). Would be nice to see more focus on this in the examples if that's the case.