input: Write a function to calculate the maximum, minimum and mean number of elements in a given string. The function should return a tuple containing the maximum element, minimum element, and mean element of the string. 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(string.encode()) / num_elements
      return (max_element, min_element, mean_element)
  
  assert get_stats_for_string("abcdef")==('f', 'a', 98.0)
  assert get_stats_for_string("12345")==('5', '1', 53.0)
  assert get_stats_for_string("")==(None, None, None)
  assert get_stats_for_string("a")==('a', 'a', 97.0)
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)