return proxyClass.isInstance(arg)
        // Equal proxy instances should mostly be instance of proxyClass
        // Under some edge cases (such as the proxy of JDK types serialized and then deserialized)
        // the proxy type may not be the same.
        // We first check isProxyClass() so that the common case of comparing with non-proxy objects
        // is efficient.

    return new SerializedForm<>(delegate());
  }

  private void readObject(ObjectInputStream stream) throws InvalidObjectException {
    throw new InvalidObjectException("Use SerializedForm");
  }

  /** Serialized form of the map, to avoid serializing the constraint. */
  private static final class SerializedForm<B extends @Nullable Object> implements Serializable {
    private final Map<Class<? extends @NonNull B>, B> backingMap;

  }

  @GwtIncompatible // SerializableTester
  public void testSerializable() {
    Multiset<Color> ms = EnumMultiset.create(asList(Color.RED, Color.YELLOW, Color.RED));
    assertEquals(ms, SerializableTester.reserialize(ms));
  }

  public void testEntrySet() {
    Multiset<Color> ms = EnumMultiset.create(Color.class);
    ms.add(Color.BLUE, 3);
    ms.add(Color.YELLOW, 1);
    ms.add(Color.RED, 2);

  @GwtIncompatible // SerializableTester
  public void testLexicographicalComparatorSerializable() {
    Comparator<byte[]> comparator = SignedBytes.lexicographicalComparator();
    assertThat(SerializableTester.reserialize(comparator)).isSameInstanceAs(comparator);
  }

  public void testSortDescending() {
    testSortDescending(new byte[] {}, new byte[] {});
    testSortDescending(new byte[] {1}, new byte[] {1});