@Rifah_Maulidya, I received your code and it looks perfect, the problem is in the notebook itself.
I want you to:
1-Click File → Open
2-check box before your notebook file. After it is selected, delete it.
3-Upload this notebook instead and fill the graded function with yours.
PS: make sure the name is C1W1_Assignment.ipynb and nothing else, otherwise the submission will fail.
C1W1_Assignment.ipynb (4.3 KB)
This has happened before to somebody else on C1W2.