input: Write a function to calculate the maximum, minimum, and mean number of elements in a given string and return them as a tuple. If the given string is empty then return None.
  
  def get_stats_from_string(string):
      if not string:
          return None
      num_elements = len(string)
      max_element = max(string)
      min_element = min(string)
      mean_element = sum(map(ord, string)) / num_elements
      return (max_element, min_element, mean_element)
  
  assert get_stats_from_string("abcdef")==('f', 'a', 100.0)
  assert get_stats_from_string("123456")==('6', '1', 52.5)
  assert get_stats_from_string("AaBbCc")==('c', 'A', 79.5)
  assert get_stats_from_string("")==None
output: def get_stats_from_string(string):
      if not string:
          return None
      num_elements = len(string)
      max_element = max(string)
      min_element = min(string)
      mean_element = sum(map(ord, string)) / num_elements
      return (max_element, min_element, mean_element)