title: Get model ManyToManyField's through class manager
body: <p>Considering  this model structure:</p>
  
  <pre><code>class Playlist(models.Model):
      track_list = models.ManyToManyField('Track', blank=True, through='TrackToPlaylist')
  
  
  class Track(models.Model):
      artist = models.CharField(max_length=128)
  
  class TracktoPlaylistManager(models.Manager):
      def get_ordered_tracks(self):
          return sorted(self.get_queryset(), key=lambda x: x.votes_balance, reverse=True)
  
  class TracktoPlaylist(models.Model):
     track = models.ForeignKey(Track)
     playlist = models.ForeignKey(Playlist)
  
     objects = TracktoPlaylistManager()
  
     @property
     def votes_balance(self):
         # here's order calculated
         return
  </code></pre>
  
  <p>I would like to access through model's manager to get sorted tracks for Playlist object. but Playlist.objects.first().track_list is a ManyToManyFieldManager object. <code>Playlist.objects.first().track_list.through.objects</code> returns this manager but i would have to filter instances  by Playlist... which is double work. </p>