models.py

class Publisher(CBModel):
    class Meta:
        abstract = True

    doc_type = 'publisher'
    id_prefix = 'pub'
    bucket = "MAIN_BUCKET"

    name = models.CharField(max_length=45, null=True, blank=True)

class Book(CBModel):
    class Meta:
        abstract = True

    doc_type = 'book'
    id_prefix = 'bk'
    bucket = "MAIN_BUCKET"

    name = models.CharField(max_length=45, null=True, blank=True)
    pages = models.IntegerField()
    publisher = ModelReferenceField(Publisher)