docs: public VoltXMLElement voltAnnotateWindowedAggregateXML(VoltXMLElement exp, SimpleColumnContext context)
              throws HSQLParseException {
          VoltXMLElement winspec = new VoltXMLElement("winspec");
          exp.children.add(winspec);
          if (m_partitionByList.size() > 0) {
              VoltXMLElement pxe = new VoltXMLElement("partitionbyList");
              winspec.children.add(pxe);
              for (Expression e : m_partitionByList) {
                  pxe.children.add(e.voltGetXML(context, null));
              }
          }
  
          VoltXMLElement rxe = new VoltXMLElement("orderbyList");
          winspec.children.add(rxe);
  
          if (m_sortAndSlice != null) {
              for (int i = 0; i < m_sortAndSlice.exprList.size(); i++) {
                  Expression e = (Expression) m_sortAndSlice.exprList.get(i);
                  assert(e instanceof ExpressionOrderBy);
                  ExpressionOrderBy expr = (ExpressionOrderBy)e;
                  VoltXMLElement orderby = expr.voltGetXML(context, null);
                  boolean isDescending = expr.isDescending();
                  orderby.attributes.put("descending", isDescending ? "true": "false");
                  rxe.children.add(orderby);
              }
          }
          return exp;
      }