code: public static void register(Class<?> clazz, Function<Object, ?> converter) {
        if (clazz == null || converter == null) {
           log.warn("Trying to register either a null class ({0}) or a null converter ({1}). Ignoring!",
                    clazz,
                    converter);
           return;
        }
        converters.put(clazz, converter);
     }
docs: Register void.
  
  @param clazz     the clazz
  @param converter the converter