function SkipUntilObservable(source, other) {
      this._s = source;
      this._o = isPromise(other) ? observableFromPromise(other) : other;
      this._open = false;
      __super__.call(this);
    }
Merges an observable sequence of observable sequences into an observable sequence.
@returns {Observable} The observable sequence that merges the elements of the inner sequences.