python抽象基类可以从C扩展继承吗？

好像当我有一个继承自gevent.Greenlet的抽象基类(它继承自C扩展模块greenlet:https://github.com/python-greenlet/greenlet)时,实现它的类不会引发任何关于未实现方法的abc错误.

class ActorBase(gevent.Greenlet):
    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def foo(self):
        print "foo"

class ActorBaseTest(ActorBase):
    def bar(self):
        print "bar"

abt = ActorBaseTest()  # no errors!

如果我从object它继承失败按预期方式:

class ActorBase(object):
    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def foo(self):
        print "foo"

class ActorBaseTest(ActorBase):
    def bar(self):
        print "bar"

>>> abt = ActorBaseTest()
Traceback (most recent call last):
  File "/home/dw/.virtualenvs/prj/local/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 2827, in run_code
exec code_obj in self.user_global_ns, self.user_ns
  File "", line 1, in 
    abt = ActorBaseTest()
TypeError: Can't instantiate abstract class ActorBaseTest with abstract methods foo

实现此功能的正确方法是什么？