Why does this JSON code not work in Swift 3.2 -

i on final leg of first part of app. have been following tutorial exactly, every single article find has achient code. anyway, am, , receiving 2 errors have never seen before.

these erors: 1. use of unresolved identifer mutablecontainers 2. argument in call

any appreciated. have changed url names privacy.

 // send user data server side     let myurl = nsurl(string:   "https://www.nyserver.com/userregister.php");     let request = nsmutableurlrequest(url:myurl! url);     request.httpmethod = "post";      let poststring = "email=\(string(describing: useremail))&password=\(string(describing: userpassword))";      request.httpbody = poststring.data(using: string.encoding.utf8);       let task = urlsession.shared.datatask(with: request urlrequest) {         data, response, error in          if error != nil {             print("error=\(string(describing: error))")             return         }          var err: nserror?         var json = jsonserialization.jsonobjectwithdata(data, options: .mutablecontainers, &error) as? nsdictionary          if let parsejson = json {             var resultvalue = parsejson["status"] as? string             print("result: \(resultvalue)")              var isuserregistered:bool = false;             if(resultvalue=="sucess") { isuserregistered = true; }              var messagetodisplay:string = parsejson["message"] string!;             if(!isuserregistered)             {                 messagetodisplay = parsejson["message"] string!;             }               dispatchqueue.main.async(execute: {                  //display alert messagewith confirmation.                 var myalert = uialertcontroller(title:"alert", message:messagetodisplay, preferredstyle: uialertcontrollerstyle.alert);                  let okaction = uialertaction(title:"ok", style:uialertactionstyle.default){ action in                     self.dismiss(animated: true, completion:nil);                 }                  myalert.addaction(okaction);                 self.present(myalert, animated:true, completion:nil);             });          }       }      task.resume()