public static ItemSpec<String> item(String key, @Nullable String value) {
    return item(key, Type.STRING, value);
  }
@Test
  public void testItemEquality() {
    new EqualsTester()
        .addEqualityGroup(DisplayData.item("foo", "bar"), DisplayData.item("foo", "bar"))
        .addEqualityGroup(DisplayData.item("foo", "barz"))
        .testEquals();
  }