public Publisher<K> keyIterator() {
        return keyIterator(null);
    }
@Test
    public void testPutAll() {
        RMapRx<Integer, String> map = redisson.getMap("simple");
        sync(map.put(1, "1"));
        sync(map.put(2, "2"));
        sync(map.put(3, "3"));

        Map<Integer, String> joinMap = new HashMap<Integer, String>();
        joinMap.put(4, "4");
        joinMap.put(5, "5");
        joinMap.put(6, "6");
        sync(map.putAll(joinMap));

        assertThat(toIterator(map.keyIterator())).toIterable().contains(1, 2, 3, 4, 5, 6);
    }