title: Celery: How to retrieve metadata from custom states?
body: <p>The example for custom states show that metadata can be stored:
  <a href="http://docs.celeryproject.org/en/latest/userguide/tasks.html#custom-states">http://docs.celeryproject.org/en/latest/userguide/tasks.html#custom-states</a></p>
  
  <p>Which API can I use to retrieve the metadata associated with a result?</p>