Python3.7 cannot unpickle `snmachine/example_data/example_test_dataset.pckl` (in `examples/example_plasticc.ipynb`)

[aseyffert]

Cannot complete execution in the examples/example_plasticc.ipynb notebook due to incompatible pickle protocol used when creating snmachine/example_data/example_test_dataset.pckl.

To Reproduce:

1. Create python environment in accordance with environment.yml and requirements.txt.
2. Install jupyter via python -m pip install jupyter.
3. Open examples/example_plasticc.ipynb as a jupyter notebook.
4. Execute the cells sequentially up to and including the first one in the Choose the Photometric Redshift section.

System Information:

• Operating System: Fedora Linux 39
• snmachine Version: 2.0.0.post3
• Occurred on which branch and with what commit: [master-ab2074b]