UserWarning: Importing 'grader_labextension' outside a proper installation

[Paul2708]

Describe the bug
Running JupyterLab with this extension yields the following warning during startup:

/tmp/warning/.venv/lib/python3.12/site-packages/grader_labextension/__init__.py:9: UserWarning: Importing 'grader_labextension' outside a proper installation.
  warnings.warn("Importing 'grader_labextension' outside a proper installation.")

To Reproduce

1. Create and activate a clean Python virtual environment.
2. Install the latest packages using pip install jupyterlab grader_labextension
3. Run JupyterLab using python -m jupyterlab
4. See error in JupyterLab logs.

Expected behavior
No warning should appear.