You can clone with
In chapter "Classes and Objects", the "Inheritance" section uses Emplyee/Programmer/Cook/Baker/GeekCook as example.
The problem with is that it's pretty arbitrary, there doesn't seem to be an problem it actually solves. One doesn't know what behavior to expect from the classes, since there's no use case.
Instead a problem should be stated, to which a rather natural solution involves inheritance and polymorphism.
See also: http://lists.canonical.org/pipermail/kragen-tol/2011-August/000937.html
Perhaps we could steal Jonathan's travel agency example?