@Override
    public String lowerKey(String key) {
        return complete(treeMap.lowerKey(key));
    }
@Test(expected = ConsistentMapException.Timeout.class)
    public void testTimeout() {
        ConsistentTreeMapWithError<String> consistentMap =
                new ConsistentTreeMapWithError<>();
        consistentMap.setErrorState(TestingCompletableFutures.ErrorState.TIMEOUT_EXCEPTION);
        DefaultConsistentTreeMap<String> map =
                new DefaultConsistentTreeMap<>(consistentMap, 1000);

        map.lowerKey(KEY1);
    }