ZK - Open Source Ajax Java Framework

i download pivottable from http://www.zkoss.org/download/zkpivottable,and get pivottable.jar import to project,use demo code meet less some TabularPivotModel class function like

model.addField
model.addColumnField("Airline");
model.addColumnField("Flight");
model.addRowField("Agent");
model.addRowField("Customer");
model.addDataField("Price");
model.addDataField("Mileage");

code is
private static void fillRemainingFields(TabularPivotModel model) {
for(String name : getColumns())
if(model.getField(name) == null)
model.addField(name, -1, null); // problem line,less addField function

please help!!!