@Override
    @SuppressWarnings("unchecked")
    public <K> K getCurrentKey() {
        return (K) currentKeySupplier.get();
    }
@Test
    void testGetCurrentKey() {
        final String key = "key";
        DefaultStateManager stateManager =
                new DefaultStateManager(
                        () -> key,
                        ignore -> {},
                        new MockStreamingRuntimeContext(false, 1, 0),
                        new MockOperatorStateStore());
        assertThat((String) stateManager.getCurrentKey()).isEqualTo(key);
    }