code: public static Rollbar init(Config config) {
      if (notifier == null) {
  
        synchronized (Rollbar.class) {
          if (notifier == null) {
            notifier = new Rollbar(config);
            LOGGER.debug("Rollbar managed notifier created.");
          }
        }
      }
  
      return notifier;
    }
docs: Method to initialize the library managed notifier instance.
  
  @param config the configuration.
  @return the library managed instance.