社交网络授权Tornado.auth

Question

首先，抱歉我的英语不好。我需要使用tornado.auth在社交网络中编写应用程序授权。但我无法理解tornado.auth文档中的示例如何工作，例如Facebook。

Class FacebookGraphLoginHandler (tornado.web.RequestHandler,
                                tornado.auth.FacebookGraphMixin):
  @ tornado.gen.coroutine
  def get (self):
      if self.get_argument ( "code", False):
          user = yield self.get_authenticated_user (
              redirect_uri = '/ auth / facebookgraph /',
              client_id = self.settings [ "facebook_api_key"],
              client_secret = self.settings [ "facebook_secret"],
              code = self.get_argument ( "code"))
          # Save the user with e.g. set_secure_cookie
      else:
          yield self.authorize_redirect (
              redirect_uri = '/ auth / facebookgraph /',
              client_id = self.settings [ "facebook_api_key"],
              extra_params = { "scope": "read_stream, offline_access"}) 

什么＆＃39;代码＆＃39;？从社交网络返回哪种形式的数据？我该如何处理它？如果您也为Google+解释，那会很好，因为您只能从g +获取access_token，我的理解方式。感谢