text: import {Observable} from 'rxjs/Observable';
  import 'rxjs/add/observable/timer';
  import 'rxjs/add/operator/startWith';
  
  const original$ = Observable.timer(1000, 1000);
  const result$ = original$.startWith('start');
  
  result$.subscribe(
    console.log,
    null,
    () => console.log('complete')
  );
  
  
  