Fix is_isomorphous

[kmdalton]

As discussed in #277 , DataSet.is_isomorphous currently does not do what is indicated in its docstring. This change makes the behavior in line with the expectation that cell_threshold is a percent difference.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.98%. Comparing base (b78e571) to head (2222d77).
Report is 64 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #279      +/-   ##
==========================================
- Coverage   91.22%   88.98%   -2.25%     
==========================================
  Files          37       40       +3     
  Lines        2531     2841     +310     
==========================================
+ Hits         2309     2528     +219     
- Misses        222      313      +91     

Flag	Coverage Δ
unittests	88.98% <100.00%> (-2.25%)	⬇️

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[tjlane]

Bug is fixed.

I'd like to see a (regression) test for this method added before merging, to ensure it stays fixed.

[kmdalton]

as requested, @tjlane

[tjlane]

Nice! Logic looks solid. A few comments in the interest of people who might read this code in the future.

Also: do we need a test for the spacegroup comparison bit?

[kmdalton]

@tjlane , space groups are tested in test_is_isomorphous. I don't think there is any point in doing it for this test too.

[tjlane]

love it

[tjlane]

thanks for tackling this one @kmdalton !