static <A> Map<S, A> subMapWithKeysStartingWithIC(S prefix, Map<S, A> map) {
  if (empty(prefix) || empty(map)) ret map;
  if (map instanceof NavigableMap && isCIMap(map)) {
    ret ((NavigableMap) map).subMap(prefix, true, lexicographicallyNextString(prefix), false);
  }
  ret filterKeys(swic$(prefix), map);
}