在多重繼承時尋找一個重載方法的順序（MRO）來自於C3算法，
方法是進行迭代：
class B(A1,A2,A3 ...)
這時B的mro序列 mro(B) = [B] + merge(mro(A1), mro(A2), mro(A3) ..., [A1,A2,A3，...])
當調用super（B，self）.fun（）時會按照上述順序調用各個父類的方法，一直到當某個類沒有調用super方法爲止
C3具體算法實現如下：
from exceptions import Exception
def c3_lineration(kls):
if len(kls.__bases__) == 1:
return [kls, kls.__base__]
else:
l = [c3_lineration(base) for base in kls.__bases__]
l.append([base for base in kls.__bases__])
return [kls] + merge(l)
def merge(args):
if args:
for mro_list in args:
for class_type in mro_list:
for comp_list in args:
if class_type in comp_list[1:]:
break
else:
next_merge_list = []
for arg in args:
if class_type in arg:
arg.remove(class_type)
if arg:
next_merge_list.append(arg)
else:
next_merge_list.append(arg)
return [class_type] + merge(next_merge_list)
else:
raise Exception
else:
return []
class A(object):pass
class B(object):pass
class C(object):pass
class E(A,B):pass
class F(B,C):pass
class G(E,F):pass
print c3_lineration(G)