Have the student re-run all the code cells in the notebook from the top down. That's likely to fix the issue 🙂
For extra context: When you save your work in a notebook, it will save your writing/code, but it won't save the data or memory stored in the notebook. So, each time you open it, you have to re-run all the cells from the top-down to re-download the coursekata package, re-download the dataset, etc. Re-running will restore all the memory and it will now be able to find example_dat , thereby resolving the "not found" error. Let me know if that works!
P.S. A shortcut for re-running all the code cells top-down is to click on "Kernel" and click "Restart & Run All"
![After The AP Data Science Challenge [Teacher Forum]](https://dschallengeteachers.freeflarum.com/assets/logo-024smqgu.png){kind=logo}