Sequence arg = getArgument(0).eval(docs, contextSequence, contextItem);
Sequence arg = getArgument(0).eval(contextSequence, contextItem);
	public Sequence eval(DocumentSet docs, Sequence contextSequence, Item contextItem)		throws XPathException {		Sequence arg = getArgument(0).eval(docs, contextSequence, contextItem);		if (arg.getLength() == 0)			return Sequence.EMPTY_SEQUENCE;		DurationValue duration = (DurationValue) arg.itemAt(0);		return new DecimalValue(Double.toString(duration.getSeconds()));	}