private <T extends LinkOrResource> void addMulti(
String name, Collection<? extends T> res, Map<String, T> rs, Map<String, List<T>> multiRs) {
List<T> resource = res == null ? new LinkedList<>() : new LinkedList<>(res);
if (rs.containsKey(name)) resource.add(rs.get(name));
List<T> links = multiRs.get(name);
if (links == null) {
multiRs.put(name, resource);
} else {
links.addAll(resource);
}
}
