How to use the @lumino/messaging.MessageLoop.postMessage function in @lumino/messaging

if (previousTitle) {
      previousTitle.owner.hide();
    }

    // Show the current widget.
    if (currentTitle) {
      currentTitle.owner.show();
    }

    // Flush the message loop on IE and Edge to prevent flicker.
    if (Platform.IS_EDGE || Platform.IS_IE) {
      MessageLoop.flush();
    }

    // Schedule an emit of the layout modified signal.
    MessageLoop.postMessage(this, Private.LayoutModified);
  }

addWidget(widget: Widget, options: DockPanel.IAddOptions = {}): void {
    // Add the widget to the layout.
    if (this._mode === 'single-document') {
      (this.layout as DockLayout).addWidget(widget);
    } else {
      (this.layout as DockLayout).addWidget(widget, options);
    }

    // Schedule an emit of the layout modified signal.
    MessageLoop.postMessage(this, Private.LayoutModified);
  }

private _evtMouseUp(event: MouseEvent): void {
    // Do nothing if the left mouse button is not released.
    if (event.button !== 0) {
      return;
    }

    // Stop the event when releasing a handle.
    event.preventDefault();
    event.stopPropagation();

    // Finalize the mouse release.
    this._releaseMouse();

    // Schedule an emit of the layout modified signal.
    MessageLoop.postMessage(this, Private.LayoutModified);
  }

protected onChildRemoved(msg: Widget.ChildMessage): void {
    // Ignore the generated tab bars.
    if (Private.isGeneratedTabBarProperty.get(msg.child)) {
      return;
    }

    // Remove the widget class from the child.
    msg.child.removeClass('p-DockPanel-widget');

    // Schedule an emit of the layout modified signal.
    MessageLoop.postMessage(this, Private.LayoutModified);
  }

private _onTabMoved(): void {
    MessageLoop.postMessage(this, Private.LayoutModified);
  }