docs: def get_access_token(self):
          """
          Obtain the access token to access private resources at the API
          endpoint.
          """
          if self.access_token is None:
              request_token = self._get_rt_from_session()
              oauth = OAuth1(
                  self.consumer_key,
                  client_secret=self.consumer_secret,
                  resource_owner_key=request_token['oauth_token'],
                  resource_owner_secret=request_token['oauth_token_secret'])
              at_url = self.access_token_url
              # Passing along oauth_verifier is required according to:
              # http://groups.google.com/group/twitter-development-talk/browse_frm/thread/472500cfe9e7cdb9#
              # Though, the custom oauth_callback seems to work without it?
              oauth_verifier = get_request_param(self.request, 'oauth_verifier')
              if oauth_verifier:
                  at_url = at_url + '?' + urlencode(
                      {'oauth_verifier': oauth_verifier})
              response = requests.post(url=at_url, auth=oauth)
              if response.status_code not in [200, 201]:
                  raise OAuthError(
                      _('Invalid response while obtaining access token'
                        ' from "%s".') % get_token_prefix(
                            self.request_token_url))
              self.access_token = dict(parse_qsl(response.text))
  
              self.request.session['oauth_%s_access_token' % get_token_prefix(
                  self.request_token_url)] = self.access_token
          return self.access_token