title: How to find out and unsubscribe from topics on Firebase - iOS?
body: <p>I'm using Firebase on iOS and am trying to implement Topics. I know how to subscribe and unsubscribe:</p>
  
  <pre><code>Messaging.messaging().subscribe(toTopic: "myTopic")
  
  Messaging.messaging().unsubscribe(fromTopic: "myTopic")
  </code></pre>
  
  <p>My question is, how do I know what topics I am subscribed to? How do I unsubscribe to all topics I am subscribed to? How do I access all topics from Firebase?</p>