public static String historyToken(ResourceId instanceId) {
   return "i/" + instanceId.asString();
 }
 public static SafeUri safeUri(ResourceId id, PageId pageId) {
   return UriUtils.fromTrustedString("#" + pageId + "/" + id.asString());
 }
 @Override
 public String serializeAsHistoryToken() {
   return instanceId.asString();
 }
 @Override
 public InstancePlace parse(String token) {
   return new InstancePlace(ResourceId.valueOf(token), pageId);
 }
 public FormResource(String resourceId) {
   this.resourceId = ResourceId.valueOf(resourceId);
 }