code: def callback_oauth2(self, request):
          
          callback_url = self.callback_url(request)
  
          oauth = OAuth2Session(client_id=self.consumer_key, redirect_uri=callback_url, scope=self.scope)
          request_token = oauth.fetch_token(self.REQ_TOKEN,
                                            code=request.GET.get('code', ''),
                                            authorization_response=callback_url,
                                            client_secret=self.consumer_secret,
                                            scope=self.scope,
                                            verify=False)
          return request_token.get('access_token')
docs: Process for oAuth 2
              :param request: contains the current session
              :return: