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