docs: public static <E> List<E> clean(List<E> list) {
          if (iterable(list)) {
              return list.stream().filter(e -> {
                  if (Objects.isNull(e)) {
                      return false;
                  }
                  if (e instanceof Nullable) {
                      return !((Nullable) e).isNull();
                  }
                  return true;
              }).collect(Collectors.toList());
          }
          return list;
      }