input: def get_max_min(lst: List[int]) -> Tuple[int, int]:
      """
      Get the maximum and minimum values in a given list.
      >>> get_max_min([1, 2, 3, 4, 5])
      (1, 5)
      >>> get_max_min([-1, -2, -3, -4, -5])
      (-5, -1)
      >>> get_max_min([0, 0, 0, 0])
      (0, 0)
      """
output:     if not lst:
          return (None, None)
      max_val = min_val = lst[0]
      for num in lst:
          if num > max_val:
              max_val = num
          if num < min_val:
              min_val = num
      return (min_val, max_val)