code: def set_ioloop(self, ioloop=None):
          
          self._server.set_ioloop(ioloop)
          self.ioloop = self._server.ioloop
docs: Set the tornado IOLoop to use.
  
          Sets the tornado.ioloop.IOLoop instance to use, defaulting to
          IOLoop.current(). If set_ioloop() is never called the IOLoop is
          started in a new thread, and will be stopped if self.stop() is called.
  
          Notes
          -----
          Must be called before start() is called.