static SchemaNode parseRankingExpression(ParseContext context, SchemaNode node, List<Diagnostic> diagnostics) {
        String expressionString = node.getRankExpressionString();

        Position expressionStart = node.getRange().getStart();
        
        if (expressionString == null)return null;
        CharSequence sequence = expressionString;

        RankingExpressionParser tolerantParser = new RankingExpressionParser(context.fileURI(), sequence);
        tolerantParser.setParserTolerant(true);

        try {
            if (node.isASTInstance(consumedExpressionElm.class)) {
                tolerantParser.expression();
            } else {
                tolerantParser.featureList();
            }
        } catch (ai.vespa.schemals.parser.rankingexpression.ParseException pe) {
            // Ignore
        } catch (IllegalArgumentException ex) {
            // Ignore
        }

        if (tolerantParser.rootNode() == null) return null;
        return new SchemaNode(tolerantParser.rootNode(), expressionStart);
    }
SchemaRankExpressionParser is a parser for rank epxressions, which is small part in other files
integration/schema-language-server/language-server/src/main/java/ai/vespa/schemals/schemadocument/SchemaRankExpressionParser.java