finallytry adding some new features to the three designs whatever features strike your fancy are fine ' like to see way to differentiate between available and unavailable propertiesfor starters it' not of much use to me if it' already rentedwhich design is easiest to extendwhich is hardestif somebody asked you why you thought thiswould you be able to explain yourselfsummary we've gone from simple inheritanceone of the most useful tools in the object-oriented programmer' toolboxall the way through to multiple inheritanceone of the most complicated inheritance can be used to add functionality to existing classes and builtins using inheritance abstracting similar code into parent class can help increase maintainability methods on parent classes can be called using super and argument lists must be formatted safely for these calls to work when using multiple inheritance in the next we'll cover the subtle art of handling exceptional circumstances