def submit(self, func: Callback, *args, **kargs) -> None:
        self.tasks.put((func, args, kargs))

    def wait_completion(self) -> None:
        self.tasks.join() ----- ➍

def cpu_waster(i: int) -> None:
    name = current_thread().getName()
    print(f"{name}: 작업 {i}를 수행 중")
    time.sleep(3)

def main() -> None:
    pool = ThreadPool(num_threads=5) ----- ➎

➏

    for i in range(20): 
        pool.submit(cpu_waster, i)

    print("모든 작업 요청이 전달됨")
    pool.wait_completion()