BUG: GH12622 where pprint of Timestamp in nested structure fails
- [x] closes #12622
- [x] tests added / passed
- [x] passes `git diff upstream/master | flake8 --diff`
- [x] whatsnew entry

I suspect this is a bug in Cython (I don't think `type(A).func` should be an `instancemethod`).  Not sure if we should use this workaround as we encounter issues in the wild, or do this for all the functions we can think of.
