getArgument(0).eval(docs, contextSequence).toNodeSet();
getArgument(0).eval(contextSequence).toNodeSet();
	public Sequence eval(		DocumentSet docs,		Sequence contextSequence,		Item contextItem)		throws XPathException {		Node n = null;		if (contextItem != null)			contextSequence = contextItem.toSequence();		if (getArgumentCount() > 0) {			NodeSet result =				getArgument(0).eval(docs, contextSequence).toNodeSet();			if (result.getLength() > 0)				n = result.item(0);		} else {			if (contextSequence.getLength() > 0				&& contextSequence.getItemType() == Type.NODE)				n = ((NodeSet) contextSequence).item(0);		}		if (n != null) {			switch (n.getNodeType()) {				case Node.ELEMENT_NODE :				case Node.ATTRIBUTE_NODE :					return new StringValue(n.getNamespaceURI());				default :					return new StringValue("");			}		}		return new StringValue("");	}