title: Access many-to-many related to the same model
body: <p>I have a movie database with has following models. I store the director details in Actor model itself. That is I create an actor and then link him as director. Through this I can get the director who is also an actor. Now my problem is to list all the directors. I am not able write the query. I get ReverseManyRelatedObjectsDescriptor most of the time.</p>
  
  <pre><code>class Actor(models.Model):
      actorid = models.AutoField(primary_key=True)
      name = models.CharField(max_length=250)
      sex = models.CharField(max_length=1)
  
      def director_list(self):
          directors = self.filter(actor__in=Movie.director).distinct()
                          **#ReverseManyRelatedObjectsDescriptor error**
          return directors
  
  
  class Movie(models.Model):
      movieid = models.AutoField(primary_key=True)
      title = models.CharField(max_length=250)
      actor = models.ManyToManyField(Actor, related_name="actor")
      director= models.ManyToManyField(Actor, related_name="director")
  </code></pre>
  
  <p>Please help, thanks in advance.</p>