input: Write a python function to get statistics for a string containing ASCII values.
  assert get_stats_for_string("abcdef") == ('f', 'a', 99.5)
  assert get_stats_for_string("xyz") == ('z', 'x', 121.0)
  assert get_stats_for_string("hello") == ('o', 'e', 106.2)
output: def get_stats_for_string(s):
      max_char = max(s)
      min_char = min(s)
      average_ascii = sum(ord(char) for char in s) / len(s)
      return (max_char, min_char, average_ascii)