@rhettinger Could you advise about the API of this function? I think the new API is more convenient but a bit less powerful, but I am waiting for your input on this matter to continue development/discussion :)

Just to make it simpler to evaluate. The equivalent input for:

['ABDGI', 'BEG', 'CEH', 'KCFHJ']

would be:

{'I': {'G'},
 'G': {'D', 'E'},
 'D': {'B'},
 'B': {'A'},
 'E': {'B', 'C'},
 'H': {'E', 'F'},
 'J': {'H'},
 'F': {'C'},
 'C': {'K'}}

and the result is:

[{'A', 'K'}, {'B', 'C'}, {'D', 'E', 'F'}, {'G', 'H'}, {'I', 'J'}]

representing that you can choose an arbitrary order in every group and that satisfies the sorting.

@tim-one @larryhastings The PR has been still for a while and I think is close to being ready for a first merge. I would like to get this in before the 3rd alpha so there is plenty of time to test this and still have possibilities to change things. Do you have any changes to the API that you would like to be changed? What about Larry's paint cans? 😆

Improvement to the docs can be made later as this can always be modified freely after the feature freeze :)

Now that the CycleError exception is now documented, I will go ahead and land this as I indicated in #11583 (comment). Let's open new, more focused PRs for documentation improvements, the bikeshedding stuff (looking at you @larryhastings 😉 ) and any other minor stuff. I will leave the issue open until we are completely happy with all aspects.

Thank you very much to everyone involved in this issue, the discussions and for all the patience with reviews and iterations (thanks to @tim-one especially 👌 ).