docs: public void removeNotificationHandler(String serviceName, NotificationHandler handler){
  
          ServiceInstanceUtils.validateServiceName(serviceName);
          if (handler == null) {
              throw new ServiceException(ErrorCode.SERVICE_DIRECTORY_NULL_ARGUMENT_ERROR,
                      ErrorCode.SERVICE_DIRECTORY_NULL_ARGUMENT_ERROR.getMessageTemplate(),
                      "NotificationHandler");
          }
    
          synchronized(notificationHandlers){
              if(notificationHandlers.containsKey(serviceName)){
                  List<NotificationHandler> list = notificationHandlers.get(serviceName);
                  if(list.contains(handler)){
                      list.remove(handler);
                  }
                  if(list.isEmpty()){
                      notificationHandlers.remove(serviceName);
                  }
              }
          }
      }