public static <T extends Writable> WritableCoder<T> of(Class<T> clazz) {
    return new WritableCoder<>(clazz);
  }
@Test
  public void testNullWritableEncoding() throws Exception {
    NullWritable value = NullWritable.get();
    WritableCoder<NullWritable> coder = WritableCoder.of(NullWritable.class);

    CoderProperties.coderDecodeEncodeEqual(coder, value);
  }