Reindexes an item from an old key to a new key. If there was no such
item, does nothing. Returns 0 if successful, else -1.

def rename(self, old_key, new_key):
        """
        Reindexes an item from an old key to a new key. If there was no such
item, does nothing. Returns 0 if successful, else -1.
        """
        return lib.zhashx_rename(self._as_parameter_, old_key, new_key)