How to set Debug mode in Tornado?

I googled and found a hint that I should set debug mode in Tornado so that it could reload files automatically on update. But I didn't find an exact string to insert. I tried different combinations similar to this application.settings = {"Debug": True} but it doesn't help.


Here's a tweaked example from the tornado site:

if __name__ == "__main__":
    application = tornado.web.Application([
        (r"/", MainHandler) 
    ], debug=True)
    application.listen(8888)
    tornado.ioloop.IOLoop.instance().start()