DocumentSet docs,
	public Sequence eval(		DocumentSet docs,		Sequence contextSequence,		Item contextItem)		throws XPathException {		if(contextItem != null)			contextSequence = contextItem.toSequence();		Sequence seq = getArgument(0).eval(docs, contextSequence, contextItem);		return seq.getLength() == 0 ? BooleanValue.TRUE : BooleanValue.FALSE;	}