This is ready for review and comment. Without review, I will merge this after at least 12 hours, no sooner than Thu 08 Aug 18:00 GMT (13:00 my local).

I'll follow that quickly with a PR to do a 0.3.1 patch release.

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (4a9d497) to head (b653f4c).

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##              main       #82   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files          110       110           
  Lines         5422      5422           
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  Hits          5422      5422           

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I think the issue here is that we don't do the all-optionals test when we do release testing. So we didn't trigger the code to import OpenMM (which is what this is about).

FWIW, we can also simplify the OpenMM code in there. Treating OpenMM with the rules of either SPEC0 or NEP29, we no longer need to support OpenMM 7.5.