Angular 5 to 6 Upgrade: Property 'map' does not exist on type Observable : <p>Ive upgraded my angular application from version 5 to 6 and im getting this error from the following code.</p>

<pre><code>  const request = this.evidenceService.get().map((res) =&gt; res.data)
                .catch(error =&gt; Observable.of(null));
</code></pre>

<blockquote>
  <p>Property 'map' does not exist on type 'Observable'.</p>
</blockquote>
