input: Write a python function to find the minimum and maximum values in a list.
  assert find_min_max([3, 7, 1, 12, 5]) == (1, 12)
  assert find_min_max([10, 20, 30, 40, 50]) == (10, 50)
  assert find_min_max([-10, 0, 10, 20, 30]) == (-10, 30)
output: def find_min_max(lst):
      if not lst:
          return None, None
      return min(lst), max(lst)