title: Property 'collection' does not exist on type 'AngularFireDatabase'?
body: <p>While hovering on collection I am getting this error</p>
  <p><strong>Property 'collection' does not exist on type 'AngularFireDatabase'</strong></p>
  <p><a href="https://i.stack.imgur.com/LHmYN.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/LHmYN.png" alt="enter image description here" /></a></p>
  <pre><code>this.db.collection(&quot;cities&quot;).doc(&quot;LA&quot;).set({
        name: &quot;Los Angeles&quot;,
        state: &quot;CA&quot;,
        country: &quot;USA&quot;
    })
    .then(function() {
        console.log(&quot;Document successfully written!&quot;);
    })
    .catch(function(error) {
        console.error(&quot;Error writing document: &quot;, error);
    });
  </code></pre>
  <p>I have already imported this</p>
  <pre><code>import { AngularFireDatabase } from &quot;@angular/fire/database&quot;;
  </code></pre>