title: Filter to show sub tasks of a filtered list of parent tasks
body: <p>I have a JIRA filter which returns all the fixes in a future release:</p>
  
  <p><code>project = MyProject AND fixVersion = "1.1.1" and issuetype in standardIssueTypes() and status != Closed</code></p>
  
  <p>All of these issues have Sub-Tasks which I want to have in a new filter result. They do not have the <code>fixVersion</code> set.</p>
  
  <p>I have tried the <code>parent</code> filter but this only accepts Key or ID.</p>
  
  <p>Is there any way I can write a filter to access these without manually using something like <code>parent in (MyProject-1,MyProject-2,MyProject-3,MyProject-4,etc)</code>?</p>