python multiprocessing pool(进程池)报错：pool objects cannot be passed between processes or pickled

pool objects cannot be passed between processes or pickled

class Test(object):
    def run(self):  
        self.pool=Pool(2)
        self.pool.apply_async(func,(xx,xx))

    def __getstate__(self):
        self_dict = self.__dict__.copy()
        del self_dict['pool']

        return self_dict

    def __setstate__(self, state):
        self.__dict__.update(state)
        

class Test(object):
    def run(self):  
        from pathos.multiprocessing import ProcessPool
        self.pool=ProcessPool(2)
        # apipe 就是 apply_async
        self.pool.apipe(func,(xx,xx))