`UnmodifiableMultimap.forEach` uses the `Multimap.forEach` default implementation which involves listing entries, and creating a new lambda instead of simply passing the BiConsumer through to the protected instance. This is safe to pass directly though because `forEach(BiConsumer)` is a read-only operation.
public static Ordering<Object> arbitrary() {
    return ArbitraryOrderingHolder.ARBITRARY_ORDERING;
  }
  private static class ArbitraryOrderingHolder {
    static final Ordering<Object> ARBITRARY_ORDERING = new ArbitraryOrdering();
  }
  @VisibleForTesting
  static class ArbitraryOrdering extends Ordering<Object> {
    private final AtomicInteger counter = new AtomicInteger(0);
    private final ConcurrentMap<Object, Integer> uids =
        Platform.tryWeakKeys(new MapMaker()).makeMap();
    private Integer getUid(Object obj) {
      Integer uid = uids.get(obj);
      if (uid == null) {
        
        
        
        uid = counter.getAndIncrement();
        Integer alreadySet = uids.putIfAbsent(obj, uid);
        if (alreadySet != null) {
          uid = alreadySet;
        }
      }
      return uid;
    }
    @Override
    public int compare(Object left, Object right) {
      if (left == right) {
        return 0;
      } else if (left == null) {