如何在进程池中让子进程创建新的子进程？

import multiprocessingimport osclass CustomManager(multiprocessing.Manager):    def __init__(self):        super().__init__()        self.lock = self.Lock()        self.process_count = 0    def create_process(self, target, args=(), kwargs={}):        self.lock.acquire()        # 记录当前已创建的子进程数        self.process_count += 1        # 创建子进程        p = self.Process(target=target, args=args, kwargs=kwargs)        p.start()        # 释放锁        self.lock.release()        return pif __name__ == '__main__':    # 创建定制的Manager    manager = CustomManager()    # 将定制的Manager传递给进程池    pool = multiprocessing.Pool(processes=10, manager=manager)    # 在子进程中创建新的子进程    def create_new_process(msg):        # 获取定制的Manager        manager = multiprocessing.current_process().manager        # 创建新子进程        p = manager.create_process(os.system, args=("echo {}".format(msg),))        # 等待新子进程结束        p.join()    # 将任务添加到进程池    for i in range(20):        pool.apply_async(func=create_new_process, args=(str(i),))    # 关闭进程池    pool.close()    pool.join()    # 输出创建子进程的总数    print('Total sub-processes created:', manager.process_count)