Fix: Test for legacy mudata .h5mu files

[votti]

Background

I noticed that mudata currently has issues to load legacy .h5mu files generated
by mudata==0.1.2

Changes

• Adds test files for .h5mu from mudata==0.1.2
• Adds a test that generally handles regression testing against files from older versions
• Adds fix for loading .h5mu from mudata==0.1.2

[votti]

PR #87 is required to fix the underlying build failure. Happy to rebase once this PR is merged.

[gtca]

Thank you, @votti!

The suggested tests will probably not be run by CI anyway?

I refactored the code a bit more in b87797e to be concise there and yet to include the suggested way to handle None.

[votti]

The testfile would be small and would have run as part of CI.

If this kind of regression tests make sense depends on the scope of the project: if it is a priority that old (published?) mudata files should be readable by the latest version, tests like these would be valuable.

[gtca]

Thanks, @votti, that's definitely in scope and will be valuable to have.

The testfile would be small and would have run as part of CI.

I am currently not sure we want to start including actual hdf5 files in contrast to generating them, which would not be executed by the CI (if I understand it correctly). We would then also need to include MuData files populated with different attributes beyond the simplest case with two modalities with no annotations.

Let's continue discussing that in #92!