来看例子：
class A:
def apam(self, c='1'):
print('A.spam'+c)
class B(A):
def spam(self,c='2'):
print('B.spam')
super(B, self).apam(c='3') # is the same as 'super().apam(c='3')'
B().spam()
B().apam()
B().spam('4')
B().apam('5')
输出是：
assert B.spam A.spam3
assert A.spam1
assert B.spam A.spam3
assert A.spam5
