How to inject meta data in existing object

Sometimes, i need to change existing method behaviour or inject meta data for testing purpouses. Like: we have 2 predefined classes which we can't change (we can implement SomeClass* just to ease injecting metadata).

class A(SomeClass1):
    def __init__(self):
        last_id = self.id

class B(SomeClass2):
   def __init__(self):
        last_id = self.id

So what should be done to next line print incremented id's (like: 1 2 3) ?

print A().id, B().id, A().id