class Rights {

    public Rights removeEntriesFor(Username username) {
        return new Rights(
            rights.asMap()
                .entrySet()
                .stream()
                .filter(entry -> !entry.getKey().equals(username))
                .flatMap(entry -> entry.getValue()
                    .stream()
                    .map(v -> Pair.of(entry.getKey(), v)))
                .collect(Guavate.toImmutableListMultimap(Pair::getKey, Pair::getValue)));
    }

    @JsonCreator public  Rights(Map<Username, List<Right>> rights);
    private  Rights(Multimap<Username, Right> rights);

}