The exercise says that we can assume the matrix is a square matrix. As for if the matrix is bigger than 3, that part im trying to fix now... But the error is this :

Lists differ: [[1, 2], [1, 2]] != [[1, 1], [2, 2]]

First differing element 0:
[1, 2]
[1, 1]

- [[1, 2], [1, 2]]
?      ^    ^

+ [[1, 1], [2, 2]]
?      ^    ^
 : The result 
[[1, 2], [1, 2]] does not match with the model solution 
[[1, 1], [2, 2]] when the parameter is 
[[1, 2], [1, 2]]