> Now, how important do you think type consistency is?  when using
> iterators, does one ever look at it and test its type?  if this is
> important, I _could_ take another look at dicts and seta and create
> fresh iterators to the dicts and sets made out of the remainder of the
> items, rather than iterators to lists.

I think type consistency is important if it can be achieved reasonably
simply.
In the dict and set case, I'm not sure you can recreate the internal
table in the same order (even accross interpreter restarts). In this
case, you should just check that the unpickled data is a subclass of
collections.abc.Iterator.