Message 208475 - Python tracker

Sounds reasonable - we'll need that to convert range() and slice()
anyway (I totally failed at finding time to look at the builtins this
weekend, but I'd still like to handle those before the 3rd beta).

An alternative would be to actually add "ParameterGroup" as a new
class that contains parameters (assuming tuple isn't sufficient), so
the structure of the parameters more directly matches the underlying
signature.