done = function() {
    if (!apiclient.authTokenRefresher_) {
      apiclient.setAuthTokenRefresher(function(authArgs, refresherCallback) {
        /** @type {!TokenClient} */
        const tokenClient =
            goog.global['google']['accounts']['oauth2']['initTokenClient']({
              'client_id': authArgs.client_id,
              'callback': refresherCallback,
              'scope': authArgs.scope,
            });
        tokenClient.requestAccessToken();
      });
    }
    callback();
  }
Ensures that the Google Identity Services (GIS) libraries are loaded.
@param {function()} callback The function to call when the library is ready.
@private