title: Retrieving GroupResult from taskset_id in Celery?
body: <p>I am starting a set of celery tasks by using celery group as described in the <a href="http://celery.github.com/celery/userguide/tasksets.html#groups" rel="noreferrer">official documentation</a></p>
  
  <p>I am also storing the group (taskset) id into a db, in order to poll celery for the taskset state.</p>
  
  <pre><code>job = group([
          single_test.s(1, 1),
          single_test.s(1, 2),
          single_test.s(1, 3),
      ])
  
  result = job.apply_async()
  
  test_set = MyTestSet()
  test_set.taskset_id = result.id
  
  # store test_set into DB
  </code></pre>
  
  <p>Is there a way to obtain a GroupResult object (i.e. my <code>result</code>) starting from the taskset id?
  Something like what is done in <a href="https://stackoverflow.com/questions/5544611/retrieve-a-task-result-object-given-a-task-id-in-celery">this question</a>, but working with celery groups.</p>
  
  <p>I already tried doing:</p>
  
  <pre><code>r = GroupResult(taskset_id)
  </code></pre>
  
  <p>but it does not work, as <code>r.results()</code> is always empty.</p>
  
  <p>Should I use <code>GroupResult.save()</code> and <code>GroupResult.restore()</code> <a href="http://docs.celeryproject.org/en/master/reference/celery.result.html#celery.result.GroupResult" rel="noreferrer">methods</a>?</p>