Influence for sentiment analysis notebook

[Xuzzo]

Description

This PR closes #452

Changes

• Adds new notebook, influence_sentiment_analysis.ipynb, which showcases ekfac for LLMs
• Fixes small issue in Ekfac implementation
• Adds methods to EkfacInfluence that return influence values for each layer
• Adds tests for new by_layer methods

Checklist

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

[schroedk]

You have to add the new notebook to the mkdocs.yml

      - For sentiment analysis: examples/influence_sentiment_analysis.ipynb

[AnesBenmerzoug]

Sorry for the late review. Overall it looks good to me.
Feel free to merge it once the comments I left are addressed.

[AnesBenmerzoug]

I just had a look at the rendered notebook in the documentation and some things are off:

• The table of content in the beginning doesn't render properly

• Plotting code should be hidden using the 'hide-input' tag