new_contents: import json
  
  import tornado.ioloop
  import tornado.web
  
  class MainHandler(tornado.web.RequestHandler):
      """Handles post requests by responding with a JSON file."""
      @tornado.web.asynchronous
      def post(self):
          data = json.loads(self.request.body.decode('utf-8'))
          self.optimize_portfolio(data)
          self.finish()
  
      def optimize_portfolio(self, data):
          Info = {'key': 'value'}
          self.write(json.dumps(data))
  
  def make_app():
      """Returns an application with a handler for only '/'."""
      return tornado.web.Application([
          (r"/", MainHandler),
      ])
  
  if __name__ == "__main__":
      app = make_app()
      app.listen(8000)
      tornado.ioloop.IOLoop.current().start()
      """
      Responds to this curl
  
      curl -H "Content-Type: application
  /json" -X POST -d '{"username":"xyz","password":"xyz"}' http://localhost:8000
      """
  
subject: Write a tornado server that responds to POST requests.