Also note that this patch will not sort sequences of mixed types where
some types are intercomparable "correctly" (in the way that Python 2
did), e.g. for

{1:2, 2:3, 'a':4, 1.5: 5}

the 1.5 key will not be placed between the 1 and 2 keys.

I'm not aware of a way to implement that behavior without support for a
general comparison function instead of a DSU key function.