class Account(object):
    def __init__(self):
        self.bag = []
    def get_total(self):
        return sum(self.bag)
    def add(self, banknote):
        self.bag.append(banknote)
    total = property(get_total)

class SubAccount(Account):
    def fun(self):
        if self.total < 17:
            print "I want more cards."
        else:
            print "I am done."