public Sequence eval(StaticContext context, DocumentSet docs, Sequence contextSequence, Item contextItem) { return new BooleanValue(true);
public Sequence eval(DocumentSet docs, Sequence contextSequence, Item contextItem) { return BooleanValue.FALSE;
	public Sequence eval(StaticContext context, DocumentSet docs, Sequence contextSequence, 		Item contextItem) {		return new BooleanValue(true);	}