input: Write a function to calculate the maximum, minimum, and mean number of elements in a given string. Return these values as a tuple. If the string is empty, return None.
  
  def analyze_string_elements(s):
      if not s:
          return None
      max_element = max(s)
      min_element = min(s)
      mean_element = sum(map(ord, s)) / len(s)
      return (max_element, min_element, mean_element)
  
  assert analyze_string_elements("abcdef") == ('f', 'a', (97+98+99+100+101+102)/6)
  assert analyze_string_elements("hello") == ('o', 'e', (104+101+108+108+111)/5)
  assert analyze_string_elements("") == None
  assert analyze_string_elements("a") == ('a', 'a', 97/1)
output: def analyze_string_elements(s):
      if not s:
          return None
      max_element = max(s)
      min_element = min(s)
      mean_element = sum(map(ord, s)) / len(s)
      return (max_element, min_element, mean_element)