@Test
  public void testOptionalExtends() {
    Predicate<Number> predicate = n -> n.toString().equals("0");
    OptionalExtends t = OptionalExtends.builder().setPredicate(predicate).build();
    Truth.assertThat(t.predicate()).hasValue(predicate);
  }
Tests that an annotation on a type parameter of an {@code @AutoValue} builder is copied to the
implementation class.
value/src/it/functional/src/test/java/com/google/auto/value/AutoValueJava8Test.java