How can I make my app accept certain photos file extensions?

Question

I want my app to accept certain image extensions(png, jpg,.....) otherwise, it should show an error message.

import UIKit
import Photos

class ViewController: UIViewController {
    
    @IBOutlet var imageView: UIImageView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
    }
    

    
    @IBAction func didTapCamera(){
        let picker = UIImagePickerController()
        picker.sourceType = .camera
        picker.allowsEditing = true
        picker.delegate = self
        present(picker, animated: true)
    }

    
    
    @IBAction func didTapButton(){
        let picker = UIImagePickerController()
        picker.sourceType = .photoLibrary
        picker.delegate = self
        picker.allowsEditing = true
        present(picker, animated: true)
      }
    
}
    extension ViewController: UIImagePickerControllerDelegate, UINavigationControllerDelegate{
        func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
            if let image = info[UIImagePickerController.InfoKey(rawValue: "UIImagePickerControllerEditedImage")] as? UIImage{
                imageView.image = image
            }
            picker.dismiss(animated: true, completion: nil)
    }
    
    func imagePickerControllerDidCancel(_ picker: UIImagePickerController){
                picker.dismiss(animated: true, completion: nil)
            }
}

I couldn't find any subject or code about it, I don't know why we need to request certain extensions, but it's required in my collage project.