Write a program that prints the maximum element of a square matrix below the main diagonal. The elements of the main diagonal are also taken into account.

import numpy as np
def matrix (mat):
  mat=np.array(mat)
  for i in range(len(mat)):
    for j in range(len(mat[1])):
      if i+j==len(mat)-1:
        print(max(mat[:,j]))

matrix([[1,2,3],[4,5,6],[7,8,9]])