import { Observable } from 'rxjs/Observable';import 'rxjs/add/operator/map';import 'rxjs/add/operator/catch';import 'rxjs/add/observable/throw';  updatePassenger(passenger: Passenger): Observable
     
       {    let headers = new Headers({      'Content-Type': 'application/json'    });    let options = new RequestOptions({      headers: headers    });    return this.http      .put(`${PASSENGER_API}/${passenger.id}`, passenger, options)      .map((response: Response) => response.json())      .catch((error: any) => Observable.throw(error.json()));  }