title: Using a system supplied NSValueTransformer on a transformable Core Data attribute
body: <p>When trying to use a system supplied <code>NSValueTransformer</code> in Core Data I get the following warning:</p>
  
  <pre><code>Warning: no NSValueTransformer with class name 'NSKeyedUnarchiveFromDataTransformerName' was found for attribute 'someAttribute' on entity 'SomeEntity'
  </code></pre>
  
  <p>How come the <code>NSKeyedUnarchiveFromDataTransformer</code> is not recognized?</p>