input: def get_stats_for_string(string):
      """
      Calculate the maximum, minimum and mean number of elements in a given string.
      Here, we assume that implicitly 'elements' refer to characters in the string.
      
      >>> get_stats_for_string("abcdef")
      ('f', 'a', 100.0)
      >>> get_stats_for_string("12345")
      ('5', '1', 54.0)
      >>> get_stats_for_string("")
      (None, None, None)
      """
      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)
output:     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)