问与rxjs有关的错误(6) "switchMap不是函数“

EN

 return auth.refreshToken().switchMap((token) => {
                if (token) {

                    return next.handle(this.addToken(req));
                }

                // If we don't get a new token, logout.
                auth.logoutUser(0);
                return empty;

            }).catch((e: any) => {
                // If there is an exception calling 'refreshToken', logout.
                auth.logoutUser(0);
                return empty;
            }).finally(() => {
                this.isRefreshingToken = true;
            });

"ApiService::handleError TypeError: auth.refreshToken(...).switchMap is not a function
".

 return auth.refreshToken().pipe(switchMap((token) => {
                if (token) {

                    return next.handle(this.addToken(req));
                }

                // If we don't get a new token, logout.
                auth.logoutUser(0);
                return empty;

            }).catch((e: any) => {
                // If there is an exception calling 'refreshToken', logout.
                auth.logoutUser(0);
                return empty;
            }).finally(() => {
                this.isRefreshingToken = true;
            });

Argument of type '(token: {}) => Observable<HttpEvent<any>> | ((scheduler?: SchedulerLike) => Observable<never>)' is not assignable to parameter of type '(value: {}, index: number) => ObservableInput<HttpEvent<any>>'."

import { switchMap } from "rxjs/operators"; to 
import 'rxjs/add/operator/switchMap'; 

 return this.tokenSubject.pipe(
                filter(token => token != null),
                take(1),
                switchMap(token => {
                    return next.handle(this.addToken(req));
                })
            );