@classmethod
    def _cache_key(cls, pk, db):
        key_parts = ('o', cls._meta, pk, 'default')
        return ':'.join(map(encoding.smart_unicode, key_parts))
Custom django-cache-machine cache key implementation that avoids having
dataset/ETHPy150Open mozilla/addons-server/src/olympia/amo/models.py/ModelBase._cache_key