Option to output datasets

[aulemahal]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes Return Datasets #1257
• Tests for the changes have been added (for bug fixes / features)
  • (If applicable) Documentation has been added / updated (for bug fixes / features)
• CHANGES.rst has been updated (with summary of main changes)
  • Link to issue (:issue:number) and pull request (:pull:number) has been added

What kind of change does this PR introduce?

• New option : as_dataset. When True, indicators return Datasets instead of DataArrays or tuples thereof.

Does this PR introduce a breaking change?

No.

Other information:

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB

[Zeitsperre]

Cool!

Is there a particular reason why we wouldn't want to offer this as a method/call signature of Indicator objects? e.g. some_indicator(..., as_dataset=True)?

[aulemahal]

It's simply that I didn't want to add another argument to the indicators, as to now overcrowd the signature with parameters that do not impact the computation itself.

But, it could be done easily.

[Zeitsperre]

That's a good point. The workflow example is clear enough, so I don't see any harm from keeping this as an option set via context.

The only other way I could see this being implemented (for conventional xarray users, anyway) would involve extending xarray.DataArray.to_dataset(), but that could be either very easy or an absolute nightmare. Is extending a DataArray class method an acceptable/desirable thing to do?

[tlogan2000]

LGTM ... I think the context / set_options mode is a decent compromise

[Zeitsperre]

New black came out. I'll see what can be done.

[aulemahal]

Oh! I thought this was a python 3.8 issue...

[Zeitsperre]

FYI: https://github.com/psf/black/releases/tag/24.1.0

Looks like a bunch of breaking changes. I think I'm going to pin black to the pre-commit latest version so we don't run into this again. Will happen in a new PR.