Fix indexing on axis keys using generic map (related to spatial averaging)

[tomvothecoder]

Description

• Closes spatial_average not interpreting latitude #163

Summary of Changes

• Add GENERIC_AXES_MAP for mapping CF compliant keys to their generic representations
• Add _get_generic_axis_keys() for proper indexing in spatial averaging methods
• Update bounds methods to use GENERIC_AXES_MAP
• Update incorrect axis refs to axis

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

If applicable:

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass with my changes (locally and CI/CD build)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have noted that this is a breaking change for a major release (fix or feature that would cause existing functionality to not work as expected) -- will include notes in next minor release instead

[tomvothecoder]

Hi @pochedls, this PR is ready for review.

It fixes #163, KeyError: "The data variable 'tas' is missing a 'lat' dimension, which is required for spatial averaging.". Basically, your example datasets use the CF long key "latitude" instead of the short key "lat" without a proper mapping of "lat" to "latitude". CF-xarray can't interpret "lat" as being "latitude" when retrieving the coordinates and bounds, so it fails (it finds "latitude" and "latitude " when you check the keys with ds.cf.keys()).

My solution is to use a map of CF long and short keys to their generic versions for a more robust retrieval of coordinates. For example, "lat" and "latitude" maps to "Y", which CF-xarray can interpret agnostically if the CF attribute Axis: "Y" is set.

[codecov-commenter]

Codecov Report

Merging #172 (5ceb932) into main (69dd39d) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #172   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            7         8    +1     
  Lines          369       381   +12     
=========================================
+ Hits           369       381   +12     

Impacted Files	Coverage Δ
xcdat/axis.py	100.00% <100.00%> (ø)
xcdat/bounds.py	100.00% <100.00%> (ø)
xcdat/spatial_avg.py	100.00% <100.00%> (ø)
xcdat/xcdat.py	100.00% <100.00%> (ø)

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[pochedls]

Should this be "axis" (singular)?

[pochedls]

Hi Tom - this works and looks good to me. I didn't understand why you swapped axis / axes - it seemed like it may have made more sense before (looping over each axis (singular) in axes (plural)).

[tomvothecoder]

Thanks Steve, I think I got carried away with my find and replace and forgot the definition of axis/axes again for the 10th time. I pushed a fix, but I'll search again just in case.