replace mothod for only one object but not for a class

[Christian Heimes]

Bruno Desthuilliers wrote:
> If the class is a new-style one [1], it just requires invoking the 
> descriptor protocol by yourself to get a bound method, ie:

Another note about new style classes:
You can NOT overwrite most magic methods (__*__) on the instance. Most 
magic methods are only looked up on the class object.

Christian