import { Observable } from 'rxjs/Observable';
import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import { merge } from 'rxjs';
import { of } from 'rxjs/observable/of';
import { catchError, finalize, map } from 'rxjs/operators';
import { Observable } from 'rxjs/Observable';
import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import { merge } from 'rxjs';
import { of } from 'rxjs/observable/of';
import { catchError, finalize, map } from 'rxjs/operators';