title: Django Many-To-One relationship filter set
body: <p>I have a couple models setup like so:</p>
  
  <pre><code>Group(models.Model):
      name = models.TextField(max_length=255)
  
  Thing(models.Model):
      location = models.TextField(max_length=255)
      group = models.ForeignKey(Group)
  </code></pre>
  
  <p>That's just an example to illustrate the relationship, so forgive any syntax errors.</p>
  
  <p>My question is, how can find a group which has a particular set of locations? I should be able to access the Things associated with a Group by using:</p>
  
  <pre><code>Group.thing_set
  </code></pre>
  
  <p>Right? So is there any way I can filter based on what items are within the thing_set? I'm thinking something along the lines of this.</p>
  
  <pre><code>Group.objects.filter(thing_set.location in ["Location A", "Location B"]).all()
  </code></pre>
  
  <p>Hopefully this would return to me every group which contains things from both Location A and Location B. Any suggestions or a push in the right direction would be very helpful!</p>
  
  <p>Thanks.</p>