That error from the grader is telling you that your is_overlapping function is incorrect. Please check that test cell and I’ll bet it fails in the notebook as well. It’s the very first assertion in that test cell that fails, which should be clear to debug.
All tests are passed
Then why would that test fail in the grader? Your code must be hard-coding something, e.g. referencing global variables.
Well either that or you didn’t click “Save” before you submitted to the grader and the grader is looking at an earlier version of your code. Also note that if you have renamed the notebook and are working in a renamed copy, that the grader is grading the original notebook (the one opened by “Open Notebook”).