input: Write a function to calculate the maximum, minimum, and mean number of elements in a given string. Return the results as a tuple containing the maximum element, minimum element, and mean element. If the string is empty, return (None, None, None).
  
  def get_stats_for_string(string):
      if not string:
          return (None, None, None)
      num_elements = len(string)
      max_element = max(string)
      min_element = min(string)
      mean_element = sum(ord(char) for char in string) / num_elements
      return (max_element, min_element, mean_element)
  
  assert get_stats_for_string("abcdef") == ('f', 'a', sum(ord(c) for c in "abcdef") / 6)
  assert get_stats_for_string("zxy") == ('z', 'x', sum(ord(c) for c in "zxy") / 3)
  assert get_stats_for_string("") == (None, None, None)
  assert get_stats_for_string("12345") == ('5', '1', sum(ord(c) for c in "12345") / 5)
output: def get_stats_for_string(string):
      if not string:
          return (None, None, None)
      num_elements = len(string)
      max_element = max(string)
      min_element = min(string)
      mean_element = sum(ord(char) for char in string) / num_elements
      return (max_element, min_element, mean_element)