static Map renameKeys(Map map, O... renames) {
  Map m2 = cloneMap(map);
  for (int i = 0; i+1 < l(renames); i += 2) {
    O o = map.get(renames[i]);
    if (o != null) {
      m2.remove(renames[i]);
      m2.put(renames[i+1], o);
    }
  }
  ret m2;
}