Summary

Documents difference with CPython and a document workaround provided by @anitschke.

OrderedDict.popitem() does not support the last=False argument and will always remove and return the last item if present.

closes #18370

Testing

Tested locally using sphinx-autobuild ./docs ./docs/build/html

Trade-offs and Alternatives

• no cpydiff tests has been added to avoid duplication
• the functionality could be implemented at a cost of approx 230 bytes on the unix port, but this seems quite large for a feature that is not often used , and for which a workaround is avaialable.
  OrderedDict.popitem does not support "last" keyword argument #18370 (comment)