@Test
  void emptyValueOf_nullForUndefined() throws Exception {
    assertThat(Util.emptyValueOf(Number.class)).isNull();
    assertThat(Util.emptyValueOf(Parameterized.class)).isNull();
  }
Ex. your {@code Foo} object would be null, but so would things like Number.
core/src/test/java/feign/UtilTest.java