问如何在swift中将阴影仅添加到UIVIEW顶部和底部

EN

import UIKit

class ViewController: UIViewController {
  
    
     override func viewDidLoad() {
        super.viewDidLoad()
         
        //Big container
        let container = UIView(frame: CGRect(x: self.view.bounds.width * 0.25, y: self.view.bounds.height * 0.5, width: 250, height: 290))
        container.backgroundColor = .clear
        self.view.addSubview(container)
        
        //Purple view
        let viewContainer = UIView(frame: CGRect(x: container.bounds.midX , y: 0, width: container.bounds.width * 0.89, height: container.bounds.height))

        viewContainer.layer.anchorPoint.x = 1.0

        viewContainer.backgroundColor = UIColor(displayP3Red: 158/255, green: 131/255, blue: 178/255, alpha: 1.0)
        viewContainer.layer.cornerRadius = 8
        viewContainer.clipsToBounds = true

        container.addSubview(viewContainer)

        //Gray view
        let viewContainer2 = UIView(frame: CGRect(x: container.bounds.midX , y: container.bounds.midY, width: container.bounds.width * 0.93, height: container.bounds.height * 0.86))

        viewContainer2.layer.anchorPoint.y = 1.0
        viewContainer2.layer.anchorPoint.x = 1.0


        viewContainer2.backgroundColor = UIColor(white: 0.5, alpha: 0.3)
        viewContainer2.layer.cornerRadius = 5
        viewContainer2.clipsToBounds = true

        container.addSubview(viewContainer2)
        
        //image
        let imageView = UIImageView(frame: CGRect(x: container.bounds.midX, y: container.bounds.midY, width: container.bounds.width * 0.90, height: container.bounds.height * 0.90))
        imageView.contentMode = .scaleToFill
        imageView.layer.anchorPoint = CGPoint(x: 1.0, y: 1.0)
        imageView.layer.cornerRadius = 10
        imageView.clipsToBounds = true
        imageView.image = UIImage(named: "image name")
        container.addSubview(imageView)

     }
}