Was the ipytree library already installed or did you have to install it using pip? If you had to install it we should add it as a dependency to the project. That is done in the following way:

1. Open pyproject.toml and locate the dependencies section.
2. Add a new row containing ipytree.
3. Install tox if you don't have it already: pip install tox
4. Run tox -e deps to update the dependencies.
5. When you did step (4) the dependency lists in the requirements directory were updated, we need to add and commit them to the repo: git add requirements and git commit -m "ci: tox -e deps"
6. Push the changes.