文中说：@score.setter是前一个@property装饰后的副产品。可是这个副产品是怎么来的啊，想不明白
class Student(object):
def __init__(self, name, score):
self.name = name
self.__score = score
@property
def score(self):
return self.__score
@score.setter
def score(self, score):
if score < 0 or score > 100:
raise ValueError('invalid score')
self.__score = score
