input: Write a function to calculate the maximum, minimum and mean number of elements in a given string. Return the values as a tuple (max_element, min_element, 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', 101.0)
  assert get_stats_for_string("") == (None, None, None)
  assert get_stats_for_string("zzxxaa") == ('z', 'a', 119.0)
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)