"""
Drill 4: Parent-Children-Association

Pick a concept where you can model a parent-children 
inheritance and use a child instance as attribute in another 
class' instance.

examples:
1)  Parent  : Pet
    Child   : Dog, Cat (different categories, vaccinations)
    Relation: Owner

2)  Parent  : ItemOrder
    Child   : PhoneOrder (color, specs), BookOrder(edition)
    Relation: Customer

3)  Parent  : KabaddiPlayer
    Child   : Raider, Defender (maintain different stats)
    Relation: Team

Instantiate the classes, call some view methods, get 
creative and represente your models.

"""