Working getCollection example for custom preview template

[pa-nic]

The getCollection example for custom preview templates seems not to be working;
Incorrect syntax and getCollection not available...

Can someone please provide a working example?

<script src="https://unpkg.com/decap-cms@^3.0.0/dist/decap-cms.js"></script>
<script>
  var CollectionPreview = createClass({
    render: function() {
      var entries = await getCollection('my_collection');
      var arr = [];
      entries((t) => {
        const getingData = t.get('data');
        console.log(getingData);
      });
      return null;
    }
  });

  CMS.registerPreviewTemplate("my_collection", CollectionPreview);
</script>

The goal is to display complete entries (posts) selected by a relation widget. But I can not get this basic example to work to get the entries.

Any help is appreciated. Thanks.