> With the attached patch (the patch does reintroduce the bug in 'test_incref_decref_API' of issue 22588 for testing purposes)

Sorry for not being more explicit and for being lazy doing a copy paste from msg 229022:

* this is not a patch, obviously a patch would not attempt to reintroduce a bug (as stated above), this is an experiment that you must 'patch' in order to test it (I did mention 'testing purposes' in this messagei, see above)
* this was witten in msg 229022 in answer to "Does anyone know how to automatize the dichotomy process ?" from Victor
* it only deals with subsets as a partial attempt to answer this question mostly because this is were most of the time is spent when investigating issue 22588