Remember that some public Jupyter notebook runtime environments (Google Colaboratory) cannot access other files next to the notebook, only the notebook itself.
To run a demo locally with a "standalone Jupyter", you need a fresh "venv":
[ ! -d venv ] && virtualenv -p $(which python3) venv
. venv/bin/activate
pip install --upgrade pip
pip install -r pydemolib/requirements.txt
pip install jupyterlab
You can use the same venv as mentioned above, actually. Pycharm should "just work".
Tests for all notebooks are in notebook-tests to keep this directory mostly clean.