code: private String _serializeStruct(Struct struct, Set<Object> done) throws ConverterException {
  	StringBuilder sb = new StringBuilder(goIn() + "<struct>");
  
  	Iterator<Key> it = struct.keyIterator();
  
  	deep++;
  	while (it.hasNext()) {
  	    Key key = it.next();
  	    sb.append(goIn() + "<var name=" + del + XMLUtil.escapeXMLString(key.toString()) + del + ">");
  	    sb.append(_serialize(struct.get(key, null), done));
  	    sb.append(goIn() + "</var>");
  	}
  	deep--;
  
  	sb.append(goIn() + "</struct>");
  	return sb.toString();
      }
docs: serialize a Struct
  
  @param struct Struct to serialize
  @param done
  @return serialized struct
  @throws ConverterException