the API docs note that MatchesSetwise errors if there are leftover elements, the prose story doesn't, but this is key to understanding it.
See also #826836. My preferred fix is to make the API docs on readthedocs much, much better, and kill as much of the prose docs as possible.
Bug watches keep track of this bug in other bug trackers.
See also #826836. My preferred fix is to make the API docs on readthedocs much, much better, and kill as much of the prose docs as possible.