Someone

    def tasks(self):        """Produce events until stopped"""        self.running = True        while self.running:            self.update_event.clear()            if not len(self.heap):                self.update_event.wait()            runtime, delay, queue = heappop(self.heap)            now = time()            if now < runtime:                self.update_event.wait(runtime - now)            else :                try :                    task = queue.get_nowait()                except Queue.Empty:                    continue # no pushback                else :                    yield task                    queue.task_done()            self.add(delay, queue)