如何在UILabel上制作倒影？

import UIKit

extension UILabel {
    func addReflection() {
        // 待实现
    }
}

extension UILabel {
    func addReflection() {
        let reflectionLayer = CALayer()
        reflectionLayer.frame = CGRect(x: 0, y: self.frame.height, width: self.frame.width, height: self.frame.height)
        reflectionLayer.backgroundColor = UIColor.clear.cgColor
        reflectionLayer.opacity = 0.5
        self.layer.addSublayer(reflectionLayer)
    }
}

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let label = UILabel(frame: CGRect(x: 50, y: 100, width: 200, height: 50))
        label.text = "Hello World!"
        label.textColor = .black
        label.backgroundColor = .clear
        self.view.addSubview(label)
        
        label.addReflection()
    }
}