我需要一个调度器在文本应用程序定期查询外部数据源。作为测试，我已经尝试使用APscheduler调用tick()函数每秒钟。
然而，尽管应该启动调度程序，但什么也没发生。
这是怎么回事？如何调试？

from textual.app import App, ComposeResult
from textual.containers import Horizontal, Vertical
from textual.widgets import *

from apscheduler.schedulers.background import BackgroundScheduler
 

class HeaderApp(App):
    def __init__(self, *args, **kwargs):
        self.sched = BackgroundScheduler()
        self.sched.add_job(self.tick,'interval', seconds=1)
        self.sched.start()
        super(HeaderApp, self).__init__(*args, **kwargs)
    
    def compose(self) -> ComposeResult:
        yield Header()
        yield TextLog()
        
    def tick(self):
        text_log = self.query_one(TextLog)
        text_log.write("tick")
        
    def on_mount(self):
        text_log = self.query_one(TextLog)
        text_log.write(self.sched.running)
        
if __name__ == "__main__":
    app = HeaderApp()
    app.run()