public static <K, ElemT> KeyedWorkItemCoder<K, ElemT> of(
      Coder<K> keyCoder, Coder<ElemT> elemCoder, Coder<? extends BoundedWindow> windowCoder) {
    return new KeyedWorkItemCoder<>(keyCoder, elemCoder, windowCoder);
  }
@Test
  public void testCoderProperties() throws Exception {
    CoderProperties.coderSerializable(
        KeyedWorkItemCoder.of(StringUtf8Coder.of(), VarIntCoder.of(), GlobalWindow.Coder.INSTANCE));
  }