public Set<Class<? extends SequenceListener>> getListeners(int preOrPost) {
		List<SequenceListener> toGet = null;
		if (preOrPost == PRE)
			toGet = preTrimListeners;
		if (preOrPost == POST)
			toGet = postTrimListeners;
		Set<Class<? extends SequenceListener>> set = null;
		if (toGet != null) {
			set = new HashSet<Class<? extends SequenceListener>>();
			for (SequenceListener s : toGet)
				set.add(s.getClass());
		}
		return set;
	}