DocumentSet left_docs = left.preselect(in_docs); DocumentSet right_docs = right.preselect(in_docs);
DocumentSet left_docs = left.preselect(in_docs, context); DocumentSet right_docs = right.preselect(in_docs, context);
	public DocumentSet preselect(DocumentSet in_docs) throws XPathException {        //return in_docs;		DocumentSet left_docs = left.preselect(in_docs);		DocumentSet right_docs = right.preselect(in_docs);		return left_docs.union(right_docs);	}