title: How to express a dependency graph with multiple tree roots in celery
body: <p>Let's say I have two trees which depend on a common task T:</p>
  
  <pre><code>  A       X
   / \     / \
  B   C   Y   Z
       \ /
        T
  </code></pre>
  
  <p>How may I represent such a dependency with celery primitives (<code>chain</code>, <code>group</code>, <code>chord</code>, <code>chunk</code>, etc.)?</p>
  
  <p>(Sadly, not enough points to create the tag celery, if someone could help, I'd be really grateful)</p>