text: import {Observable} from 'rxjs/Observable';
  import 'rxjs/add/observable/interval';
  import 'rxjs/add/operator/switch';
  import 'rxjs/add/operator/map';
  
  const higherOrder$ = Observable.interval(1000).map(() => Observable.interval(300));
  const result$ = higherOrder$.switch();
  
  result$.subscribe(
    console.log,
    err => console.log('Error: ', err),
    () => console.log('complete')
  );
  
  
  