old_contents: from tornado.options import options
  from tornado.ioloop import IOLoop
  from tornado.web import RequestHandler, Application
  from tornado_sqlalchemy import make_session_factory
  
  
  def do_something(session):
      pass
  
  
  class WebRequestHandler(RequestHandler):
      def get(self):
          with self.make_session() as session:
              do_something(session)
  
          self.write('Hello, World!')
  
  
  class WebApplication(Application):
      def __init__(self, *args, **kwargs):
          self.session_factory = make_session_factory(options.database_url)
  
          handlers = [
              (r'/hello', WebRequestHandler)
          ]
  
          settings = {'cookie_secret': 'hunter2'}
  
          super(WebApplication, self).__init__(handlers, **settings)
  
  
  if __name__ == '__main__':
      WebApplication().listen(8888)
      IOLoop.current().start()
  
new_contents: from tornado.options import options
  from tornado.ioloop import IOLoop
  from tornado.web import RequestHandler, Application
  from tornado_sqlalchemy import make_session_factory, SessionMixin
  
  
  def do_something(session):
      pass
  
  
  class WebRequestHandler(RequestHandler, SessionMixin):
      def get(self):
          with self.make_session() as session:
              do_something(session)
  
          self.write('Hello, World!')
  
  
  class WebApplication(Application):
      def __init__(self, *args, **kwargs):
          self.session_factory = make_session_factory(options.database_url)
  
          handlers = [
              (r'/hello', WebRequestHandler)
          ]
  
          settings = {'cookie_secret': 'hunter2'}
  
          super(WebApplication, self).__init__(handlers, **settings)
  
  
  if __name__ == '__main__':
      WebApplication().listen(8888)
      IOLoop.current().start()
  
subject: add missing import