public static <T> CollectionCoder<T> of(Coder<T> elemCoder) {
    return new CollectionCoder<>(elemCoder);
  }
@Test
  public void testCoderIsSerializableWithWellKnownCoderType() throws Exception {
    CoderProperties.coderSerializable(CollectionCoder.of(GlobalWindow.Coder.INSTANCE));
  }