How to reset a Python, Scala, or R lab in Jupyter
1. Open the recent files sidebar in the tool by clicking on the [>] button:

2. Expand the [>] twistie next to your lab notebook name. It should be at the top of the Recent Notebooks list:

3. Delete the notebook:

4. Reload the page in your browser
5. The next time you hit the Start Lab button, you should see a fresh lab