input: Write a function to get the maximum and minimum values in a given list. Return these values as a tuple.
  assert get_max_min([1, 2, 3, 4, 5]) == (1, 5)
  assert get_max_min([5, 3, 7, 1, 9]) == (1, 9)
  assert get_max_min([10, -1, 0, 4, 2]) == (-1, 10)
  assert get_max_min([1]) == (1, 1)
  assert get_max_min([]) == (None, None)
output: def get_max_min(lst):
      if not lst:
          return (None, None)
      return (min(lst), max(lst))