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