private static void add(String param, Method method, Map<String, List<Method>> map) {
        List<Method> methods = map.get(param);
        if (methods == null) {
            methods = new ArrayList<>();
            map.put(param, methods);
        }
        methods.add(method);
    }
@param fieldName     can be null -- used only for logging and debugging
@param obj
@param jsonGenerator
@throws TikaSerializationException
tika-serialization/src/main/java/org/apache/tika/serialization/TikaJsonSerializer.java