How can I upload a UIImage to an REST API using Swift, as a 'source=' parameter in swift3?

The code should like this.

        let url = URL(string: "https://api.kairos.com/v2/media")
        var urlRequest = URLRequest(url: url!)
        urlRequest.httpMethod = "POST"
        urlRequest.addValue("XXX", forHTTPHeaderField: "app_id")
        urlRequest.addValue("YYY", forHTTPHeaderField: "app_key")
        let boundary = "Boundary-\(UUID().uuidString)"
        urlRequest.setValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")


        //image data
        let image = UIImage() //replace with your image
        let fileName = "myimage.jpg"
        let data = UIImageJPEGRepresentation(image, 0.7)!

        //create body
        let body = NSMutableData()

        //append first line
        let line1_boundryPrefix = "--\(boundary)\r\n"
        body.append(line1_boundryPrefix.data(
            using: String.Encoding.utf8,
            allowLossyConversion: false)!)

        //append second line
        let line2_parameter = "Content-Disposition: form-data; name=\"source\"; filename=\"" + fileName + "\"\r\n"
        body.append(line2_parameter.data(
            using: String.Encoding.utf8,
            allowLossyConversion: false)!)

        //append third line (mime type)
        let mimeType = "image/jpg"
        let line3_contentType = "Content-Type: \(mimeType)\r\n\r\n"
        body.append(line3_contentType.data(
            using: String.Encoding.utf8,
            allowLossyConversion: false)!)

        //append image data
        //line4
        body.append(data)


        let line5 = "\r\n"
        body.append(line5.data(
            using: String.Encoding.utf8,
            allowLossyConversion: false)!)


        let line6 = "--" + boundary + "--\r\n"
        body.append(line6.data(
            using: String.Encoding.utf8,
            allowLossyConversion: false)!)
        urlRequest.httpBody = body as Data
        urlRequest.setValue(String(body.length), forHTTPHeaderField: "Content-Length")

        URLSession.shared.dataTask(with: urlRequest) { (data, urlResponse, error) in
            //handle callback
        }