title: Could not use Observable.of in RxJs 6 and Angular 6
body: <pre><code> import { Observable, of } from "rxjs";
  
  // And if I try to return like this
    return Observable.of(this.purposes);
  </code></pre>
  
  <p>I am getting an error stating, Property 'of' does not exist on type 'typeof Observable'</p>