public class Person {
  private String name;
  private String company;
  private String product;
  private String location;
  private Double income;
  private Kid kid;

public class Kid {
  private static int nextId = 0;
  private String name;
  private Integer age;
  private Date bday;

  interface KidProperties extends PropertyAccess<Kid> {
    @Path("id")
    ModelKeyProvider<Kid> key();
 
    ValueProvider<Kid, String> name();
    ValueProvider<Kid, Integer> age();
  }

private static final KidProperties props = GWT.create(KidProperties.class);
private ComboBox<Kid> comboBox;
private ListStore<Kid>kidsStore;

        RpcProxy<Object, List<Kid>> kidsProxy = new RpcProxy<Object, List<Kid>>() {
                @Override
                public void load(Object loadConfig, AsyncCallback<List<Kid>> callback) {
                    getService().loadKids(callback);
                }
            };

 final Loader<Object, List<Kid>> kidsLoader = new Loader<Object, List<Kid>>(kidsProxy );


 kidsStore= new ListStore<Kid>(kidProperties.key());

  kidsLoader .addLoadHandler(new ListStoreBinding<Object, KidProperties , List<KidProperties >>(kidsStore) {
             @Override
               public void onLoad(LoadEvent<Object, List<KidProperties>> event) {
                    super.onLoad(event);
                }
            });


comboBox= new ComboBox<KidProperties>(kidsStore, new LabelProvider<KidProperties>() {
                @Override
                public String getLabel(KidProperties item) {
                    return  item==null ? "": item.name();
                }
            });
    
            comboBox.setClearValueOnParseError(false); //  ??? <-это   зачем??
            
            comboBox.setPropertyEditor(new PropertyEditor<KidProperties >() {
                @Override
                public String render(KidProperties object) {
                    return object == null ? "" : object.getName();
                }

                @Override
                public KidProperties parse(CharSequence text) throws ParseException {
                //TODO  что тут писать??? какой код??
                    return null;
                }
            });
            comboBox.setTriggerAction(TriggerAction.ALL);

private GridEditing<Person> editing;

            editing.addEditor(comboKidColumnConfig, new Converter<????, PersonProperty>() {
                @Override
                public ???  convertFieldValue(Kid object) {
                    return object == null ? null : object.name();
                }

                @Override
                public ???  convertModelValue(???  object) {

              //TODO код ?
                    return null;
                }
       }, comboBox);