private ExpressionNode transformReference(ReferenceNode node, RankProfileTransformContext context) {
        Reference ref = node.reference();
        String name = ref.name();
        if (ref.output() != null) {
            return node;
        }
        var f = context.rankProfile().getFunctions().get(name);
        if (f != null) {
            // never transform declared functions
            return node;
        }
        return switch(name) {
            case RECIPROCAL_RANK_FUSION -> transform(expandRRF(ref), context);
            case NORMALIZE_LINEAR -> transformNormLin(ref, context);
            case RECIPROCAL_RANK -> transformRRank(ref, context);
            default -> node;
        };
    }
Recognizes pseudo-functions and creates global-phase normalizers
@author arnej
config-model/src/main/java/com/yahoo/schema/expressiontransforms/NormalizerFunctionExpander.java