def login_url(self, next="/"):

        if not self.accessToken():

            request = current.request
            session = current.session

            if not request.vars.code:

                session.redirect_uri = self.args["redirect_uri"]

                data = {"redirect_uri": session.redirect_uri,
                        "response_type": "code",
                        "client_id": self.client_id,
                        }

                if self.args:
                    data.update(self.args)

                auth_request_url = "%s?%s" % (self.auth_url,
                                              urllib.urlencode(data),
                                              )
                raise HTTP(307,
                           REDIRECT_MSG % auth_request_url,
                           Location = auth_request_url,
                           )
            else:
                session.code = request.vars.code
                self.accessToken()

        return next

    # -------------------------------------------------------------------------
Optional Hadoop ``OutputFormat`` class to write output for
dataset/ETHPy150Open sahana/eden/modules/s3oauth.py/FaceBookAccount.login_url--crossover with--dataset/ETHPy150Open Yelp/mrjob/mrjob/job.py/MRJob.hadoop_output_format