refactor: updates to backend files to match scverse template cookiecutter

[ori-kron-wis]

Formatting

• My tutorial has only one top-level (#) header

Reproducibility

• My tutorial works on Google Colab
• My tutorial sets scvi.settings.seed = 0 at the beginning of the notebook
• My tutorial has been run and includes outputs (e.g. plots, tables)

Other

• Counts and normalized data should co-exist in the datasets, see the API overview for an example
• For scRNA-seq data, normalization should be counts per median library size and then log1p transformed -- if not, a reason should be given

[Zethson]

Great, thank you very much!