PEP 467: Minor API improvements for binary sequences

This was my first thought before my head went into type systems and I changed my mind :smiley:

I guess I can be persuaded either way, so maybe don’t count my vote in any direction. I’ll settle for provoking discussion and hopefully consensus can be reached without me. (Though as an aside, I’d love more “view” type objects - C# got a huge amount of value out of their string span type, and I’d imagine we could make str[:] -> strview and bytes[:] -> bytesview pretty transparent to users.)