private static void importFunctionExpression(IntermediateOperation operation, ImportedModel model) {
        if (operation.rankingExpressionFunction().isPresent()) {
            TensorFunction<Reference> function = operation.rankingExpressionFunction().get();
            try {
                model.function(operation.rankingExpressionFunctionName(),
                               new RankingExpression(operation.rankingExpressionFunctionName(), function.toString()));
            }
            catch (ParseException e) {
                throw new RuntimeException("Model function " + function +
                                           " cannot be parsed as a ranking expression", e);
            }
        }
    }
Convert intermediate representation to Vespa ranking expressions.
model-integration/src/main/java/ai/vespa/rankingexpression/importer/ModelImporter.java