title: What does of(true) method do in Angular 7?
body: <p>I was reading from <a href="https://angular.io/guide/router#canactivate-requiring-authentication" rel="nofollow noreferrer">angular official site</a>.
  What does <strong>of(true)</strong> method mean and why it is used?  </p>
  
  <pre><code>login(): Observable&lt;boolean&gt; {
      return of(true).pipe(
        delay(1000),
        tap(val =&gt; this.isLoggedIn = true)
      );
    }
  
  </code></pre>