code: @Override
      public Filter<E> build(Level threshold) {
          return new Filter<E>() {
              @Override
              public FilterReply decide(E event) {
                  return FilterReply.NEUTRAL;
              }
          };
      }
docs: Creates a {@link Filter} that will always defer to the next Filter in the chain, if any.
  @param threshold the parameter is ignored
  @return a {@link Filter} with a {@link Filter#decide(Object)} method that will always return {@link FilterReply#NEUTRAL}.