title: How to use virtual columns in a reactive-table in meteor?
body: <p>I am using a template for columns and an object for the collection field.I want to add sub-labels for one of the columns.</p>
  
  <pre><code>settings: function() {
      return {
          collection: Template.instance().collectionObject.get("data"),
          class: "bordered striped highlight fixed",
          fields: [
              {key: "nameDate", label: "Names", tmpl: Template.nameTeleCallingReport},
              {key: "units", label: "Units", tmpl: Template.unitsTeleCallingReport},
          ],
      }
  }
  </code></pre>
  
  <p>In the second field with label "Units",  I want subheaders like: "pending, in-process and trashed". 
  In the official documentation I read about virtual coulmns. But I am unable to implement it.</p>