title: Unique collection set
body: <p>Is there a collection type that is like a table, but each row/set in the table is unique kind of like a database <code>unique</code> constraint?</p>
  <pre><code>| &quot;txt&quot; | &quot;data&quot;  |
  | &quot;txt&quot; | &quot;txt&quot;   |
  | &quot;txt&quot; | &quot;data&quot;  | // Duplicate row
  | &quot;data&quot;| &quot;txt&quot;   | // Duplicate row
  | &quot;exe&quot; | &quot;path&quot;  |
  | &quot;exe&quot; | &quot;path2&quot; |
  | &quot;exe&quot; | &quot;path&quot;  | // Duplicate row
  </code></pre>