although python' object model is straightforwardmuch of the art in oop is in the way we combine classes to achieve program' goals the next section begins tour of some of the ways larger programs use classes to their advantage oop and inheritance"is-arelationships we've explored the mechanics of inheritance in depth alreadybut ' now like to show you an example of how it can be used to model real-world relationships from programmer' point of viewinheritance is kicked off by attribute qualificationswhich trigger searches for names in instancestheir classesand then any superclasses from designer' point of viewinheritance is way to specify set membershipa class defines set of properties that may be inherited and customized by more specific sets ( subclassesto illustratelet' put that pizza-making robot we talked about at the start of this part of the book to work suppose we've decided to explore alternative career paths and open pizza restaurant (not badas career paths goone of the first things we'll need to do is hire employees to serve customersprepare the foodand so on being engineers at heartwe've decided to build robot to make the pizzasbut being politically and cybernetically correctwe've also decided to make our robot full-fledged employee with salary our pizza shop team can be defined by the four classes in the following python and example fileemployees py the most general classemployeeprovides common behavior such as bumping up salaries (giveraiseand printing (__repr__there are two kinds of employeesand so two subclasses of employee--chef and server both override the inherited work method to print more specific messages finallyour pizza robot is modeled by an even more specific class--pizzarobot is kind of chefwhich is kind of employee in oop termswe call these relationships "is-alinksa robot is chefwhich is an employee here' the employees py filefile employees py ( xfrom __future__ import print_function class employeedef __init__(selfnamesalary= )self name name self salary salary def giveraise(selfpercent)self salary self salary (self salary percentdef work(self)print(self name"does stuff"def __repr__(self)return "(self nameself salaryclass chef(employee)oop and inheritance"is-arelationships