[docs] [issue14219] make the Classes tutorial more gentle

Change by Irit Katriel iritkatriel@yahoo.com:

---------- versions: +Python 3.10, Python 3.9 -Python 2.7, Python 3.2, Python 3.3, Python 3.4

_______________________________________ Python tracker report@bugs.python.org https://bugs.python.org/issue14219 _______________________________________