如何将iOS iMessage Extension的动画与UINavigationController的动画结合在一起？

Question

在iOS iMessage Extension中，如何将MSMessagesAppViewController的演示样式更改中的动画与UINavigationController的推送动画相结合？如果尝试同时进行动画处理，则动画将不流畅且看起来也不是很好。 （我可以先制作一个动画，然后再制作另一个动画，但这会使应用感觉很慢。）

这是正常速度和慢动作的样子。

/// (Example uses the Xcode iMessage app template)
import Messages
import UIKit

class MessagesViewController: MSMessagesAppViewController {
  var nav: UINavigationController!

  override func viewDidLoad() {
    super.viewDidLoad()
    let parentVC = testViewController(title: "parent", color: .orange)
    nav = UINavigationController(rootViewController: parentVC)
    addChild(nav)
    view.addSubview(nav.view)
    nav.didMove(toParent: self)
  }

  override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesBegan(touches, with: event)

    let childVC = testViewController(title: "child", color: .purple)

    // Help! How do I animate both of these at the same time?
    requestPresentationStyle(.expanded)
    nav.pushViewController(childVC, animated: true)
  }

}


func testViewController(title: String, color: UIColor) -> UIViewController {
  let vc = UIViewController()
  vc.view.backgroundColor = color
  vc.title = title
  return vc
}