Without exclusion serializer would include forward relation twice: Normal relatation and reverse relation via intermediate model.

```
class Genre(models.Model)
  pass

class Song(models.Model)
   genres = models.ManyToMany(Genre, through='SongGenre')

class SongGenre(models.Model)
   song = models.ForeignKey(Song)
   genre = models.ForeignKey(Genre)
   is_main = models.Boolean()

class SongSerializer(ModelSerializer)
  class Meta:
    model = Song
    include_reverse_relation = True
```

With this setup SongSerializer will display `genre` field as expected but also `genre_set` field, which is just a reverse relation from `SongGenre` models `ForeignKey(Song)` field. So my code currently excludes all intermediate models if they are specified in models forward relation fields.