code: function () {
          checkDisposed(this);
          if (this.isStopped) { return; }
          this.isStopped = true;
          var now = this.scheduler.now();
          this._trim(now);
          for (var i = 0, os = cloneArray(this.observers), len = os.length; i < len; i++) {
            var observer = os[i];
            observer.onCompleted();
            observer.ensureActive();
          }
          this.observers.length = 0;
        }
docs: Notifies all subscribed observers about the end of the sequence.