class ConcurrentHashMultimap implements Multimap<K, V> {

    @Override
    public boolean containsValue(@Nullable Object value) {
        if (value == null) {
            return false;
        }
        final Object id = valueIdentityExtractor.apply((V) value);
        return entries.entrySet().stream().map(Map.Entry::getValue).anyMatch(values -> values.containsKey(id));
    }

    public  ConcurrentHashMultimap(ValueIdentityExtractor<V> valueIdentityExtractor, ConflictResolver<V> conflictResolver);

}