new_contents: import time
  from tornado.web import Application, RequestHandler
  from tornado.gen import coroutine, Task
  from tornado.ioloop import IOLoop
  
  
  class DummyAPI(RequestHandler):
      @coroutine
      def get(self):
          yield Task(IOLoop.current().add_timeout, time.time() + 1)
          self.write('Hello, World!')
          self.finish()
  
  
  if __name__ == "__main__":
      app = Application([(r"/", DummyAPI)])
      app.listen(8000)
      IOLoop.instance().start()
  
subject: Add Ex1: dummy server