如何修改imagePickerController (源摄像头)在按下“使用照片”后，直到拍摄完4张照片才会被清除？

import UIKit

class ViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
    var photoCount = 0
    
    // 拍摄按钮点击事件
    @IBAction func takePhotosButtonTapped(_ sender: UIButton) {
        let imagePickerController = UIImagePickerController()
        imagePickerController.delegate = self
        imagePickerController.sourceType = .camera
        present(imagePickerController, animated: true, completion: nil)
    }
    
    // 图片选择器完成选择后的回调方法
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
        // 处理选择的照片
        // ...
        
        // 增加已拍摄照片数量
        photoCount += 1
        
        // 判断是否已经拍摄了4张照片
        if photoCount == 4 {
            // 清除操作
            picker.dismiss(animated: true, completion: {
                // 重置照片计数器
                self.photoCount = 0
            })
        }
    }
}