input: Write a python function to return the maximum and minimum values in a list.
  assert max_min([3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]) == (9, 1)
  assert max_min([-10, -20, -30, -40, -50]) == (-10, -50)
  assert max_min([7, 7, 7, 7, 7]) == (7, 7)
  assert max_min([100, 200, 300, 400, 500]) == (500, 100)
output: def max_min(lst):
      return max(lst), min(lst)