reformatted sae_vis/data_fetching_fns.py to comply with linting rules

[shehper]

I checked that with this change, the code passes all of the following tests. I duplicated GitHub's CI workflow to make sure the versions match. Hopefully, this PR should pass the "build" tests.

poetry run ruff check && \
poetry run ruff format --check && \
poetry run pyright && \
poetry run pytest && \
poetry build

[callummcdougall]

Looks great, thanks (and sorry for the delay!)