static final Serialization.FieldSetter<? super ImmutableMultimap<?, ?>> MAP_FIELD_SETTER =
        Serialization.getFieldSetter(ImmutableMultimap.class, "map");
    static final Serialization.FieldSetter<? super ImmutableMultimap<?, ?>> SIZE_FIELD_SETTER =
        Serialization.getFieldSetter(ImmutableMultimap.class, "size");
  }

  ImmutableMultimap(ImmutableMap<K, ? extends ImmutableCollection<V>> map, int size) {

  // makes sure it is not initialized unless an instance is deserialized.
  private static class FieldSettersHolder {
    static final FieldSetter<? super ConcurrentHashMultiset<?>> COUNT_MAP_FIELD_SETTER =
        Serialization.getFieldSetter(ConcurrentHashMultiset.class, "countMap");
  }

  /**
   * Creates a new, empty {@code ConcurrentHashMultiset} using the default initial capacity, load
   * factor, and concurrency settings.
   */