'Return whether the specified `kvs_key` is set.
Arguments:
kvs_key (`DjangoKeyValueStore.Key`): The field value to delete
Returns: bool'

@contract(kvs_key=DjangoKeyValueStore.Key, returns=bool)
def has(self, kvs_key):

    return (self._cache_key_for_kvs_key(kvs_key) in self._cache)
