text: import { ping, pong } from '../redux/actions';
  import "rxjs/add/operator/mapTo";
  import "rxjs/add/operator/delay";
  
  // export const pingEpic = action$ => 
  //     action$.filter(action => action.type === actions.ping.getType())
  //         .delay(1000)
  //         .mapTo(actions.pong.raw);
  
  export const pingEpic = action$ => 
      action$.ofType(ping.getType())
          .delay(1000)
          .mapTo(pong);