class Business:
    '''An institution with some employees and an owner.'''

    def __init__(self, name, owner=None):
        self.owner = owner
        self.name = name
        self.employees = []

    def add_employee(self, employee):
        '''Add an employee to the list.'''
        self.employees.append(employee)

    def remove_employee(self, employee):
        '''Remove an employee from the list.'''
        self.employees.remove(employee)

class Restaurant(Business):
    '''A business with particular types of employees.'''

>>> fastbobs = Restaurant("Fast Bob's")
>>> fastbobs.name
"Fast Bob's"
>>> fastbobs.add_employee('Carol')
>>> fastbobs.employees
['Carol']

class Worker:
    '''A person with a job (normally).'''

    def __init__(self, name, boss, employer, salary):
        self.name = self
        self.boss = boss
        self.salary = salary
        # The employer is an instance of the Business class
        self.employer = employer

    def quit(self):
        '''Lose employer, salary, boss.'''
        self.boss = None
        self.employer = None
        self.salary = 0

class Owner(Worker):
    '''A worker who owns a business.'''

    def quit(self):
        '''Overrides Worker.quit(); the employer no longer has an owner.'''
        self.employer.owner = None
        self.employer = None
        self.salary = 0

class Worker:
    ...__init__...
    def quit(self):
        '''Lose employer and salary.'''
        self.employer = None
        self.salary = 0

class Owner(Worker):
    def quit(self):
        '''Overrides Worker.quit(); the employer no longer has an owner.'''
        self.employer.owner = None
        Worker.quit(self)

class Employee(Worker):
    def quit(self):
        '''Overrides Worker.quit(); the employee no longer has a boss.'''
        Worker.quit(self)
        self.boss = None
...        
>>> fastbobs = Restaurant("Fast Bob's")
>>> bob = Owner('Bob', None, fastbobs, 100000)
>>> fastbobs.owner = bob
>>> carol = Employee('Carol', bob, fastbobs, 10000)
>>> carol.quit()
>>> carol.boss, carol.employer, carol.salary
(None, None, 0)
>>> bob.quit()
>>> fastbobs.owner