How to apply a CIFilter to an image in Swift

import Foundation
import CoreImage
import AppKit
let nsImage = NSImage(contentsOfFile: "/Users/jim/Lenna.png")!
let cgImage = nsImage.cgImage(forProposedRect: nil, context: nil, hints: [:])!
let inputImage = CIImage(cgImage: cgImage)
let filter = CIFilter(name: "CISepiaTone")!
filter.setValue(inputImage, forKey: kCIInputImageKey)
filter.setValue(1, forKey: kCIInputIntensityKey)
let outputImage = filter.outputImage!
let rep = NSBitmapImageRep(ciImage: outputImage)
let imageData = rep.representation(using: NSBitmapImageFileType.PNG, properties: [:])!
try! imageData.write(to: URL.init(string: "file:/Users/jim/output.png")!, options: NSData.WritingOptions.atomic)