title: Django: Multiple bulk create within a transaction
body: <p>I want to do multiple bulk creates(independent) within a transaction.</p>
  
  <pre><code>            with transaction.atomic():
                  if x:
                     X.objects.bulk_create(x_objs)
                  if y:
                      Y.objects.bulk_create(y_objs)
                  if z:
                      Z.objects.bulk_create(z_objs)
  
  
  </code></pre>
  
  <p>Now I want X to rollback if Y or Z fails. How do I do that?</p>