Notebook kernel too slow (C2_W1)

Been working on C2_W1_Assignment. The first cell in Exercise 3 and the first cell in Exercise 4 (i.e., the cells you are providing solutions in) run very slowly. In fact, the Exercise 4 cells takes about 20 minutes to finish… The solution is correct. The “unittest” cell below it takes about 10 minutes to finish. Tried “restart the kernel” and “reboot the server,” but to no avail. After submitting, for “Grader timed out” error. Has anyone run into the same issue?

Closed as this is being discussed here.