// MetaTransformer that understands Transformable and List
sO lambdaMapLike metaTransform_transformableAndList() {
  ret new MetaTransformer(
    (f, o, mt) -> {
      if (o cast Transformable)
        ret o.transformUsing(mt.asFunction(f));
      null;
    });

  /*if (o cast L)
    ret map(myself, o);*/
}