$$ Code says final answer is incorrect. What is wrong with my code?

$1\mathrm{.}2[2$ pt$]$ Write a function called det$\_$and$\_$inv that takes as an input a square matrix $($a numpy array$)$ and returns a tuple with two elements $($a$)$ the determinant, and $($b$)$ the inverse if it mathematically exists and the string "does not exist" otherwise.

import numpy as np

def det$\_$and$\_$inv$($square$\_$matrix$)$:

det $=np*$ linalg.det$($square$\_$matrix$)$

try:

inv$=$np$.$linalg.inv$($square$\_$matrix$)$

except np$.$linalg.LinAlgError:

inv$=$"does not exist"

return det,inv