public void expression(String name, String expression) {
        try {
            expression = expression.trim();
            if ( expression.startsWith("file:")) {
                String filePath = expression.substring("file:".length()).trim();
                if ( ! filePath.endsWith(ApplicationPackage.RANKEXPRESSION_NAME_SUFFIX))
                    filePath = filePath + ApplicationPackage.RANKEXPRESSION_NAME_SUFFIX;
                expression = IOUtils.readFile(relativeFile(filePath, "function '" + name + "'"));
            }
            expression(name, new RankingExpression(expression));
        }
        catch (IOException e) {
            throw new IllegalArgumentException("Could not read file referenced in '" + name + "'");
        }
        catch (ParseException e) {
            throw new IllegalArgumentException("Could not parse function '" + name + "'", e);
        }
    }
Convenience method for returning a default signature
model-integration/src/main/java/ai/vespa/rankingexpression/importer/ImportedModel.java