[Python-3000] Builtin iterator type

[Bill Janssen]

> The idea of a formal interface mechanism is to have something which conveys 
> the desired information *without* all of the additional issues that come with 
> using multiple inheritance.

I hear what you're saying here, and I'm sympathetic to this.  My
question is whether it's practically possible to add another "type"
system on top of the existing one.

Bill