input: Write a python function to find the minimum and maximum values in a list.
  assert min_max([1, 2, 3, 4, 5]) == (1, 5)
  assert min_max([10, 20, 5, 7, 40, 15]) == (5, 40)
  assert min_max([-1, -5, 0, 3, 7]) == (-5, 7)
output: def min_max(lst):
      return (min(lst), max(lst))