code: public static <T> Ordering<T> explicitOrderingUnrankedFirst(
        final List<T> valuesInOrder) {
      return ImmutableExplicitOrderingNonExclusive.<T>builder()
          .rankMap(MapUtils.indexMap(valuesInOrder))
          .unrankedIsFirst(true)
          .build();
    }
docs: Like {@link Ordering#explicit(List)} but does not throw an exception when comparing
  items not explicitly ranked.  Instead, two items not explicitly ranked are considered
  equal.  Any explicitly ranked item comes after than any non-explicitly ranked item
  in the ordering.