hi am trying to create a function that would take an video URL and return the video but chopped in pieces 5 sec a piece

ViewController.swift

import UIKit
import AVFoundation
import AssetsLibrary
import MobileCoreServices
import Photos


class ViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate{
    
    //MARK: - Constants
    struct Constants {
        static let video = "Video"
        static let alertForPhotoLibraryMessage = "App does not have access to your photos. To enable access, tap settings and turn on Photo Library Access."
        static let alertForVideoLibraryMessage = "App does not have access to your video. To enable access, tap settings and turn on Video Library Access."

    }

    //click of the choose video button.
    //MARK: - THIS IS MY FUNCTION
    @IBAction func openImagePicker(_ sender: Any) {
 
        if UIImagePickerController.isSourceTypeAvailable(.photoLibrary){
            let imagePicker = UIImagePickerController()
            imagePicker.delegate = self
            imagePicker.sourceType = .photoLibrary
            imagePicker.mediaTypes = [kUTTypeMovie as String, kUTTypeVideo as String]

            let status = PHPhotoLibrary.authorizationStatus()
            switch status {
            
            case .authorized:
                imagePicker.mediaTypes = [kUTTypeMovie as String, kUTTypeVideo as String]
                print("permission granted")
                print("am in openImagePicker - status - .authorized")

            case .denied:
                print("permission denied")
                print("am in openImagePicker - status - .denied")

            case .notDetermined:
                print("Permission Not Determined")
                print("am in openImagePicker - status - .notDetermined")
                
                PHPhotoLibrary.requestAuthorization({ (status) in
                    if status == PHAuthorizationStatus.authorized{
                        // photo library access given
                        imagePicker.mediaTypes = [kUTTypeMovie as String, kUTTypeVideo as String]
                        print("access given video library")
                        print("am in openImagePicker - status - .notDetermined - PHAuthorizationStatus.authorized")

                    }else{
                        print("restriced manually")
                    }
                })
            case .restricted:
                print("permission restricted to video library")
                print("am in openImagePicker - status - .restricted")
                
            default:
                // if none of the caces are met then just go out.
                print("am in openImagePicker - status - default")
                break
            } // end switch
            
            self.present(imagePicker, animated: true, completion: nil)
        }

    }

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

    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {

        let videoURL = info["UIImagePickerControllerMediaURL"] as! URL

        
        self.cropVideo1(sourceURL1: videoURL, statTime:10.0, endTime:20.0)

 
        self.dismiss(animated: false, completion: nil)
    }
    
    func cropVideo1(sourceURL1: URL, statTime:Float, endTime:Float)
    {
        print("the Start time: \(statTime) , end time is: \(endTime)")
       
        let videoAsset: AVAsset = AVAsset(url: sourceURL1) as AVAsset
        let composition = AVMutableComposition()
        composition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: CMPersistentTrackID())
        
        let videoComposition = AVMutableVideoComposition()
        videoComposition.renderSize = CGSize(width: 1280, height: 768)
        videoComposition.frameDuration = CMTimeMake(8, 15)
        
        let instruction = AVMutableVideoCompositionInstruction()
        let length = Float(videoAsset.duration.value)
        print("length of video is: \(length)")
        
        instruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(60, 30))
        
        let start = statTime
        let end = endTime
        
        let exportSession = AVAssetExportSession(asset: videoAsset, presetName: AVAssetExportPresetHighestQuality)!
    
        exportSession.outputFileType = .mp4
        
        let startTime = CMTime(seconds: Double(start ), preferredTimescale: 1000)

        let endTime = CMTime(seconds: Double(end ), preferredTimescale: 1000)
        
        print("start time: \(startTime) end time is: \(endTime)")
        
        let timeRange = CMTimeRange(start: startTime, end: endTime)
        
        exportSession.timeRange = timeRange
        print("exportSession.timeRange : \(timeRange)")
        
        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'"
        
        let date = Date()
        
        let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString
        
        print("documentsPath : \(documentsPath)")
        
        let outputPath = "\(documentsPath)/\(formatter.string(from: date)).mp4"
        print("outputPath : \(outputPath)")
        
        let outputURL = URL(fileURLWithPath: outputPath)
        print("outputURL : \(outputURL)")

        exportSession.outputURL = outputURL
        
        exportSession.outputFileType = .mov
        print("sucess - am in cropVideo1")
        
        exportSession.exportAsynchronously(completionHandler: { () -> Void in
            DispatchQueue.main.async(execute: {
                self.exportDidFinish(exportSession)
                print("sucess am in cropVideo1-exportSession-exportAsynchronously-exportDidFinish")
                DispatchQueue.main.async(execute: {});
            })
        })
    }
    
    
    func exportDidFinish(_ session: AVAssetExportSession)
    {
        if session.status == AVAssetExportSessionStatus.completed {

            let outputURL = session.outputURL
            
            let library = ALAssetsLibrary()
            
            if library.videoAtPathIs(compatibleWithSavedPhotosAlbum: outputURL) {
                
                library.writeVideoAtPath(toSavedPhotosAlbum: outputURL) { alAssetURL, error in

                    if error != nil {
                        DispatchQueue.main.async(execute: {

                            print("exportDidFinish: Failed to save video")

                        })
                    } else {
                        DispatchQueue.main.async(execute: {

                            print("exportDidFinish: Sucessfully saved Video - exportDidFinish - else")

                        })
                    }

                }
            }
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        //self.imagePicker.delegate = self
        //give permession to access the photo gallarry.
        
        // Do any additional setup after loading the view, typically from a nib.
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}