/**
  * A method that allows you to listen to events happening in the browser.
  * Available events are: `ThemeableBrowserError`, `ThemeableBrowserWarning`, `critical`, `loadfail`, `unexpected`, `undefined`
  * @param event Event name
  * @returns {Observable<any>} Returns back an observable that will listen to the event on subscribe, and will stop listening to the event on unsubscribe.
  */
 @InstanceCheck({ observable: true })
 on(event: string): Observable<any> {
   return new Observable<any>((observer) => {
     this._objectInstance.addEventListener(event, observer.next.bind(observer));
     return () => this._objectInstance.removeEventListener(event, observer.next.bind(observer));
   });
 }

 @InstanceCheck()
 save(): Promise<any> {
   return getPromise((resolve: Function, reject: Function) => {
     this._objectInstance.save((contact: any) => {
       this._objectInstance = contact;
       resolve(this);
     }, reject);
   });
 }

 @InstanceCheck()
 clone(): Contact {
   let newContact: any = new Contact();
   for (let prop in this) {
     if (prop === 'id') return;
     newContact[prop] = this[prop];
   }
   return newContact;
 }