I’ve asked the staff to fix this.
The notebook is still missing the grader metadata for the 1st code cell in exercise 8. Please contact coursera help center to reset the workspace for you.
There is one more thing to notice about the notebook. The last execise is not done. Since you are submitting an incomplete notebook to the grader, the feedback might be incorrect. Please use #grade-up-to-here to grade an incomplete notebook.