Fix/435 broken imports

[schroedk]

Description

This PR closes #435, closes #441

Changes

• Fix issues in notebooks, due to broken imports
• Fix parsing issues for math formulas
• Remove background from plots

Checklist

• [ ] Wrote Unit tests (if necessary)
• [x] Updated Documentation (if necessary)
• [ ] Updated Changelog
• [x] If notebooks were added/changed, added boilerplate cells are tagged with "tags": ["hide"] or "tags": ["hide-input"]

[schroedk]

@schroedk Please note the instructions about notebook cells in the PR description. The new notebooks show the boilerplate and some uninformative output like progress bars.

Additionally, what is the reason to change the artist in the spotify notebook? Rihanna is still among the top values (not asking to change it back, just curious)

Other than that, I think we should merge this quickly.

Also, it would be nice to know what comes out of https://discuss.pytorch.org/t/hessian-vector-products-with-torch-func/184914

@mdbenito I revised the influence_imagenet. Not sure though, which cell to consider as boiler-plate, can you please check back on that?

When running the tests locally, I got a key error for "Rihanna", so I changed the artist.

Unfortunately, I did not get any response on the pytorch discussion forum. I will raise a bug issue on pytorch github.