def backward_eye(n):
 M = eye(n)
 for i in range(int((M.rows / 2))):
  M.row_swap((0 + i), ((M.rows - 1) - i))
 return M

def backward_eye ( n ) : M = eye ( n ) for i in range ( int ( ( M . rows / 2 ) ) ) : M . row_swap ( ( 0 + i ) , ( ( M . rows - 1 ) - i ) ) return M
returns the backward identity matrix of dimensions n x n .