id,node_id,number,state,locked,title,user,body,created_at,updated_at,closed_at,merged_at,merge_commit_sha,assignee,milestone,draft,head,base,author_association,auto_merge,repo,url,merged_by
679742895,MDExOlB1bGxSZXF1ZXN0Njc5NzQyODk1,5548,closed,0,Fix 2 type annotations in dataarray.py,28426758,"Both `set_index` and `reset_index` are wrappers to other methods that return `""DataArray""`, not `Optional[""DataArray""]`. That is, they will never return None. That's why these methods should also have only `""DataArray""` in there return signature. This way it will be possible to do something like `myarray = myarray.reset_index(...)` without getting a complaint from Mypy.

For extended discussion, see https://github.com/pydata/xarray/issues/5533#issuecomment-869822366

<!-- Feel free to remove check-list items aren't relevant to your change -->

- [x] Closes #5533
- [ ] Tests added
- [ ] Passes `pre-commit run --all-files`
- [ ] User visible changes (including notable bug fixes) are documented in `whats-new.rst`
- [ ] New functions/methods are listed in `api.rst`
",2021-06-29T09:03:23Z,2021-06-29T19:15:33Z,2021-06-29T18:51:19Z,2021-06-29T18:51:19Z,c5dbe98ce8957b6af5efa1308756296f7fa310c1,,,0,66e329974c4509f3d5aa26e264ffde8193b429f1,5ccb06951cecd59b890c1457e36ee3c2030a67aa,CONTRIBUTOR,,13221727,https://github.com/pydata/xarray/pull/5548,