title: How can I find the intersection of two Django querysets?
body: <p>I’ve got a Django model with two custom manager methods. Each returns a different subset of the model’s objects, based on a different property of the object.</p>
  
  <pre><code>class FeatureManager(models.Manager):
  
      def without_test_cases(self):
          return self.get_query_set().annotate(num_test_cases=models.Count('testcase_set')).filter(num_test_cases=0)
  
      def standardised(self):
          return self.get_query_set().annotate(standardised=Count('documentation_set__standard')).filter(standardised__gt=0)
  </code></pre>
  
  <p>(Both <code>testcase_set</code> and <code>documentation_set</code> refer to <code>ManyToManyField</code>s on other models.)</p>
  
  <p>Is there any way to get a queryset, or just a list of objects, that’s the intersectiond of the querysets returned by each manager method?</p>