Contents:
ObjectsPool
ObjectsPool.get_object()
ObjectsPool.user_supplied_callback
Observer
Subject
Subject.add()
Subject.attach()
Subject.detach()
Subject.notify()
Subject.state
Proxy
InstantiationError
SubclassRegistry
SubclassRegistry.create()
SubclassRegistry.register_as_subclass()
SubclassRegistry.subclasses
UnknownClassError