[Python-Dev] API for binary operations on Sets

[Jack Diederich]

I will say something snarky now and (hopefully) something useful tomorrow.

When ABCs went in I was +0 because, like annotations, I was told I
wouldn't have to care about them.  That said; I do actually care about
the set interface and what "set-y-ness" means for regular duck typing
reasons.  What people expect sets to do is what sets-alikes should do.

-Jack