Class mangling

Class mangling - usually a bad idea

```python
    p = CardPack()
    a = p.take(5)
```

A is a CardPack, because CardPack.take returns a CardPack() instance

    a.__class__ = PokerHand
    
Changed its nature to be a PokerHand instance instead. In this case, A gained PokerHand class methods in the process
    
    a.rank()
   
This creates A._rank, the memory of the result of A.rank()
    
    a.__class__ = CardPack

Back to a basic Card pack instance
    
    a >> p

All cards are destroyed

    a.__class__ = PokerHand

This instance of PokerHand has wrong _rank attribute.