code: def google_get_token(self, config, prefix):
          
          params = {
              'code': self.request_args_get(
                  'code',
                  default=''),
              'client_id': self.google_api_client_id,
              'client_secret': self.google_api_client_secret,
              'redirect_uri': self.scheme_host_port_prefix(
                  'http', config.host, config.port, prefix) + '/home',
              'grant_type': 'authorization_code',
          }
          payload = urlencode(params).encode('utf-8')
          url = self.google_oauth2_url + 'token'
          req = Request(url, payload)
          json_str = urlopen(req).read()
          return json.loads(json_str.decode('utf-8'))
docs: Make request to Google API to get token.