Cloneable is a marker interface that defines the contract of the Object.clone method, which is to create a
consistent copy of the instance. The clone method is not defined by the interface though, but by class Objects.
The general problem with marker interfaces is that their definitions cannot be enforced by the compiler because they have no own API. When a class
implements Cloneable but does not override Object.clone, it is highly likely that it violates the contract for
Cloneable.
