anchor.diff:    }
   
     Future removePost(String uuid) {
  -
  +    final completer = new Completer();
  +
  +    // validate uuid
  +    if (!PinUtility.isUuid(uuid)) {
  +      PinLogger.instance.shout('[CartModel] removePost: uuid format invalid: ${uuid}}');
  +      completer.complete(null);
  +    }
     }
   
     Future _addPost(String uuid, String markdown, CartPostHeader header, String html) {
  
positive.code:   Future addTag(String uuid, String name) {
      final completer = new Completer();
  
      int timestamp = PinTime.getTime();
  
      tags.addNewTag(uuid, name, timestamp: timestamp);
  
negative.code: 
    Future removeTag(String uuid) {
      final completer = new Completer();
  
      // validate uuid
      if (!PinUtility.isUuid(uuid)) {
        PinLogger.instance.shout('[CartModel] removeTag: uuid format invalid: ${uuid}}');
        completer.complete(null);
      }
  
      tags.remove(uuid, posts);
  
  