docs: public static void logExpensive(Level level, String message) {
      LogRecord rec = new ELKILogRecord(level, message);
      String[] caller = inferCaller();
      if(caller != null) {
        rec.setSourceClassName(caller[0]);
        rec.setSourceMethodName(caller[1]);
        Logger logger = Logger.getLogger(caller[0]);
        logger.log(rec);
      }
      else {
        Logger.getAnonymousLogger().log(rec);
      }
    }