How to use the onsenui/core-src/ons/ons._deviceBackButtonDispatcher function in onsenui

ons.ready(function() {
  // ons._defaultDeviceBackButtonHandler
  ons._deviceBackButtonDispatcher.enable();
  ons._defaultDeviceBackButtonHandler = ons._deviceBackButtonDispatcher.createHandler(window.document.body, () => {
    if (Object.hasOwnProperty.call(navigator, 'app')) {
      navigator.app.exitApp();
    } else {
      console.warn('Could not close the app. Is \'cordova.js\' included?\nError: \'window.navigator.app\' is undefined.');
    }
  });
  document.body._gestureDetector = new ons.GestureDetector(document.body);

  // Simulate Device Back Button on ESC press
  if (!ons.platform.isWebView()) {
    document.body.addEventListener('keydown', function(event) {
      if (event.keyCode === 27) {
        ons._deviceBackButtonDispatcher.fireDeviceBackButtonEvent();
      }
    })

document.body.addEventListener('keydown', function(event) {
      if (event.keyCode === 27) {
        ons._deviceBackButtonDispatcher.fireDeviceBackButtonEvent();
      }
    })
  }