You are using an obsolete copy of assignment. Kindly get a fresh copy and re-do your assignment.
Please refer below link comment for how to get a fresh copy.
Let me know if you still get the same error.
Also for the error which you mentioned in the first comment, it is pointing towards your input not being recalled correctly, so I would first suspect and check parse_squad grade cell as there could be some correction required on how you recalled the arguments. But in your case, first you need to do assignment on an updated assignment.
Regards
DP