Thanks for the suggestion but I’m going to decline. We has many APIS that consume an iterable and all of them do so In iteration order.  Even the regular dict() constructor takes an iterable of tuples and adds them in iteration order.  Also, I’m not concerned because of our experience with OrderedDict() which for a decade had a fromkeys() method and there has never been a question about it.   There was even an idiom for deducing a list while maintaining order: list(OrderedDict.fromkeys(seq)).