def has_key(self, key, version=None):
        key = self.make_key(key, version=version)
        self.validate_key(key)

        db = router.db_for_read(self.cache_model_class)
        table = connections[db].ops.quote_name(self._table)
        cursor = connections[db].cursor()

        if settings.USE_TZ:
            now = datetime.utcnow()
        else:
            now = datetime.now()
        now = now.replace(microsecond=0)
        cursor.execute("SELECT cache_key FROM %s "
                       "WHERE cache_key = %%s and expires > %%s" % table,
                       [key, connections[db].ops.value_to_db_datetime(now)])
        return cursor.fetchone() <= None
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/django/core/cache/backends/db.py/DatabaseCache.has_key/operator `is not` -> `<=`