out_docs = out_docs.union(getExpression(i).preselect(out_docs, context));
out_docs = out_docs.union(getExpression(i).preselect(out_docs));
    public DocumentSet preselect(DocumentSet in_docs, StaticContext context) throws XPathException {		if(getLength() == 0)			return in_docs;		DocumentSet out_docs = getExpression(0).preselect(in_docs, context);		for(int i = 1; i < getLength(); i++)			out_docs = out_docs.union(getExpression(i).preselect(out_docs, context));		return out_docs;    }