class VideoSerializer(serializers.ModelSerializer):


    class Meta:
        model = models.Video


class GalleryItemModuleSerializer(serializers.ModelSerializer):


    class Meta:
        model = models.GalleryItem

def to_representation(self, obj):
    """
        Because GalleryItem is Polymorphic
        """
if isinstance(obj, models.Photo):
    return PhotoSerializer(obj, context=self.context).to_representation(obj)
elif isinstance(obj, models.Video):
    return VideoSerializer(obj, context=self.context).to_representation(obj)
return super(GalleryItemModuleSerializer, self).to_representation(obj)
django-rest-framework + django-polymorphic ModelSerialization