public DocumentSet preselect( DocumentSet in_docs, StaticContext context ) throws XPathException {
public DocumentSet preselect( DocumentSet in_docs ) throws XPathException {
    public DocumentSet preselect( DocumentSet in_docs, StaticContext context ) throws XPathException {        DocumentSet out_docs = in_docs;        if ( predicates.size() > 0 )            for ( Iterator i = predicates.iterator(); i.hasNext();  )                out_docs = ( (Predicate) i.next() ).preselect( out_docs, context );        return out_docs;    }