public Session stopWatching(Session session) {
		watcherToUser.remove(session);
		Session clientSession = null;
		boolean deleteSet = false;
		for(Map.Entry<Session, Set<Session>> watchers : userToWatchers.entrySet()){
			if (watchers.getValue().remove(session)) {
				deleteSet = watchers.getValue().isEmpty();
				clientSession = watchers.getKey();
				break;
			}
		}
		if(deleteSet){
			userToWatchers.remove(clientSession);
		}
		return clientSession;
	}