public static <T> LengthPrefixCoder<T> of(Coder<T> valueCoder) {
    checkNotNull(valueCoder, "Coder not expected to be null");
    return new LengthPrefixCoder<>(valueCoder);
  }
@Test
  public void testRegisterByteSizeObserver() throws Exception {
    CoderProperties.testByteCount(
        LengthPrefixCoder.of(VarIntCoder.of()), Coder.Context.NESTED, new Integer[] {0, 10, 1000});
  }