How to use the @lumino/polling.Debouncer function in @lumino/polling

(msg as Widget.ChildMessage).child.removeClass(ACTIVITY_CLASS);
        this._tracker.remove((msg as Widget.ChildMessage).child);
        break;
      default:
        break;
    }
    return true;
  };

  private _activeChanged = new Signal(this);
  private _cachedLayout: DockLayout.ILayoutConfig | null = null;
  private _currentChanged = new Signal(this);
  private _dockPanel: DockPanel;
  private _isRestored = false;
  private _layoutModified = new Signal(this);
  private _layoutDebouncer = new Debouncer(() => {
    this._layoutModified.emit(undefined);
  }, 0);
  private _leftHandler: Private.SideBarHandler;
  private _restored = new PromiseDelegate();
  private _rightHandler: Private.SideBarHandler;
  private _tracker = new FocusTracker();
  private _headerPanel: Panel;
  private _topHandler: Private.PanelHandler;
  private _bottomPanel: Panel;
  private _mainOptionsCache = new Map();
  private _sideOptionsCache = new Map();
}

namespace Private {
  /**
   * An object which holds a widget and its sort rank.