$$Whats wrong with my code? Keeping getting error about D type

$1\mathrm{.}2[2pt$ 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.

$18]$ :

import numpy as $np$

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

det $=$ np$.$linalg.det square$\_$matrix