static <A> A cloneWithoutFields(A o, Set<S> fieldsToSkip) ctex {
  if (o == null) null;
  final A clone = cast nuObject(o.getClass());
  Class c = o.getClass();
  while (c != Object.class) {
    Field[] fields = c.getDeclaredFields();
    for (final Field field : fields) {
      if (contains(fieldsToSkip, field.getName())) continue;
      if ((field.getModifiers() & Modifier.STATIC) != 0) continue;
      field.setAccessible(true);
      field.set(clone, field.get(o));
    }
    c = c.getSuperclass();
  }
  return clone;
}

static <A> A cloneWithoutFields(A o, S... fieldsToSkip) {
  ret cloneWithoutFields(o, asHashSet(fieldsToSkip));
}