title: error: The element type 'Set<Marker>' can't be assigned to the set type 'Marker'
body: <p><img src="https://i.stack.imgur.com/GEJvv.png" alt="enter image description here"></p>
  
  <p>I am trying to place a marker for two purposes:</p>
  
  <ol>
  <li>Live geolocation tracking.</li>
  <li>Showing multiple markers stored in the firebase database.</li>
  </ol>
  
  <p>so inside google map widget I tried:</p>
  
  <pre><code> markers:{
      Set&lt;Marker&gt;.of(((marker != null) ? [marker] : [])), //This one for live geotracking
      Set&lt;Marker&gt;.of(markers.values), // markers stored in database
      },
  </code></pre>
  
  <p>How can I fix this?</p>