class X():
pass
class Y():
pass
class A(X, Y):
pass
assert (A, X, Y, object) == A.__mro__
class B(X, Y):
pass
assert (B, X, Y, object) == B.__mro__
class C(A, B):
pass
assert (C, A, B, X, Y, object) == C.__mro__
assert type.__mro__ == (type, object)