[Types-sig] Interface PEP

[Samuele Pedroni]

Some other motivations.

Interfaces are declarive things (aliens coming from other worlds, if you
want), proposed to support complicated designs using reflection:
not really newbies stuff, in their original worlds they are
checked against explicit declarations. I think it is better
to keep their philosophy for them.

Everything else is python runtime, algorithmic and dynamic
style.

I wonder if mixing the two just simplify implementation or really
help understanding.

My idea is that if for specifying the protocols kind of typechecking
against signatures one should write something algorithmic
costs and approach will be more clear.

regards.