Fix xarray FutureWarning about dims vs sizes

[niksirbi]

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?

pytest caught a bunch of FutureWarnings of this type:

FutureWarning: The return type of Dataset.dims will be changed to return a set of dimension names in future, in order to be more consistent with DataArray.dims. To access a mapping from dimension names to lengths, please use Dataset.sizes.

To reproduce, run pytest locally on the main branch.

What does this PR do?

For cases when we actually access a dimensions size, we now switch to using ds.sizes (which returns a dict("dim_name": dims_size)), instead of ds.dims (which will return a set of dimensions names in future).

For cases when we just need the dim names (e.g. for checking if a given dimension exists), we keep using ds.dims, which works now (because it returns the dict keys) and should continue working in the future (will return a set).

References

I think some of the "offending" uses of ds.dims where introduced in #267 and I hadn't caught them during review.

How has this PR been tested?

All test pass without warnings.

Is this a breaking change?

No.

Does this PR require an update to the documentation?

No.

Checklist:

• The code has been tested locally
• [n/a] Tests have been added to cover all new functionality
• [n/a] The documentation has been updated to reflect any changes
• The code has been formatted with pre-commit

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.77%. Comparing base (95965f8) to head (d4ec24d).
Report is 1 commits behind head on main.

Additional details and impacted files

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  Coverage   99.77%   99.77%           
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  Files          14       14           
  Lines         883      883           
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  Hits          881      881           
  Misses          2        2           

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[sfmig]

thanks @niksirbi 🚀
I added the ones from the kinematics tests - I think that should be all!