code: public void sendToAllExceptUsers(String topicURI, Object event,
  			Set<String> excludeUsers) {
  
  		Set<String> excludeSessionIds = null;
  		if (excludeUsers != null && !excludeUsers.isEmpty()) {
  			excludeSessionIds = new HashSet<>(excludeUsers.size());
  
  			for (String user : excludeUsers) {
  				for (SimpSession session : this.simpUserRegistry.getUser(user)
  						.getSessions()) {
  					excludeSessionIds.add(session.getId());
  				}
  			}
  		}
  
  		this.eventMessenger.sendToAllExcept(topicURI, event, excludeSessionIds);
  	}
docs: Send an {@link EventMessage} to every client that is currently subscribed to the
  provided topicURI except the ones listed in the excludeUsers set.
  
  @param topicURI the name of the topic
  @param event the payload of the {@link EventMessage}
  @param excludeUsers a set of users that will be excluded. If null or empty no user
  will be excluded.