input: Write a python function to rotate a matrix.
  assert rotate_matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) == [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
  assert rotate_matrix([[1, 2], [3, 4]]) == [[1, 3], [2, 4]]
  assert rotate_matrix([[1]]) == [[1]]
output: def rotate_matrix(matrix):
      return [list(row) for row in zip(*matrix)]