function asObservable(source) {
    return function subscribe(o) { return source.subscribe(o); };
  }
Merges the specified observable sequences into one observable sequence by using the selector function whenever all of the observable sequences or an array have produced an element at a corresponding index.
The last element in the arguments must be a function to invoke for each series of elements at corresponding indexes in the args.
@returns {Observable} An observable sequence containing the result of combining elements of the args using the specified result selector function.