pandas-dev#28926 Mypy fix/extension json array
ref: #28926
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

@aaditya-panik are you still working on this? Looks like there are a final few comments to address Looks like this has gone stale so closing for now but ping if you'd like to pick back up and address comments