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