public Optional<String> maybeVisit(JsonNode schema, String baseName, String name) {
            var schemaTypeText = getTypeText(schema);

            if (schemaTypeText != null && PRIMITIVE_RULES.containsKey(schemaTypeText)) {
                var rule = addPrimitive(name.equals("root") ? "root" : schemaTypeText, PRIMITIVE_RULES.get(schemaTypeText));
                return Optional.of(rule);
            }

            return Optional.empty();
        }
Converts a JSON Schema to a GBNF grammar to be used for structured output with llama.cpp.
It is a port of Python implementation from llama.cpp repository.
Current implementation doesn't support regex patterns, resolving $ref or fetching schemas from URLs.
The plan is to replace this with C++ implementation from llama.cpp though JNI.
model-integration/src/main/java/ai/vespa/llm/clients/JsonSchemaToGrammar.java