Swift 3; photo is not saving to photo gallery

This code features a special camera that features a camera with a title nested in it. So when the photo is saved to the photo gallery the title is on the photo. The camera works great but the photo is not being saved. I just need to figure out how to save the photos to the photo gallery. I did change the plist to allow access to photo gallery and camera.

 import Foundation
 import UIKit

class ViewController: UIViewController, OverlayViewControllerDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

var picker = UIImagePickerController()

@IBAction func letsDoThis(_ sender: AnyObject) {
         if UIImagePickerController.availableCaptureModes(for: .rear) != nil {
    picker = UIImagePickerController()
    picker.allowsEditing = false
    picker.sourceType = .camera
    picker.cameraCaptureMode = .photo
    picker.showsCameraControls = false
    let overlayViewController = OverlayViewController(nibName:"OverlayView", bundle: nil)
    let overlayView: OverlayView = overlayViewController.view as! OverlayView
    overlayView.frame = self.picker.view.frame

    overlayView.delegate = self

    picker.modalPresentationStyle = .fullScreen
    present(picker, animated: true, completion: {

      self.picker.cameraOverlayView = overlayView
} else {
    let alert = UIAlertController(title: "No Camera", message: "That's weird. No camera.", preferredStyle: .alert)
    let okay = UIAlertAction(title: "Alright Then.", style: .default, handler: nil)
    present(alert, animated: true, completion: nil)

 override func viewDidLoad() {
       picker.delegate = self

 override func didReceiveMemoryWarning() {
picker.dismiss(animated: true, completion: nil)

 //MARK: Image Picker Controller Delegates

 func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
let chosenImage = info[UIImagePickerControllerOriginalImage] as! UIImage
UIImageWriteToSavedPhotosAlbum(chosenImage, self,nil, nil)

    dismiss(animated: true, completion: nil)

func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
dismiss(animated: true, completion: nil)

func didCancel(overlayView: OverlayView) {
dismiss(animated: true, completion: nil)
     func didShoot(overlayView: OverlayView) {
overlayView.cameraLabel.text = "Shot Photo"
print("Shot Photo")