public static WindowedValueCoderComponents getWindowedValueCoderComponents(Coder coder) {
    checkArgument(WINDOWED_VALUE_CODER_URN.equals(coder.getSpec().getUrn()));
    return new AutoValue_ModelCoders_WindowedValueCoderComponents(
        coder.getComponentCoderIds(0), coder.getComponentCoderIds(1));
  }
@Test
  public void windowedValueCoderComponentsNoUrn() {
    thrown.expect(IllegalArgumentException.class);
    ModelCoders.getWindowedValueCoderComponents(
        Coder.newBuilder().setSpec(FunctionSpec.getDefaultInstance()).build());
  }