docs: public final void containsNoDuplicates() {
      List<Entry<?>> duplicates = newArrayList();
      for (Multiset.Entry<?> entry : LinkedHashMultiset.create(actual()).entrySet()) {
        if (entry.getCount() > 1) {
          duplicates.add(entry);
        }
      }
      if (!duplicates.isEmpty()) {
        failWithoutActual(
            simpleFact("expected not to contain duplicates"),
            fact("but contained", duplicates),
            fullContents());
      }
    }