anchor.diff:  
                 var numKeyframes = reader.readVarUint();
                 for (int l = 0; l < numKeyframes; l++) {
  -                var keyframe = readRuntimeObject<KeyFrame>(reader);
  +                var keyframe = _readRuntimeObject<KeyFrame>(reader);
                   if (keyframe == null) {
                     continue;
                   }
  
positive.code:       _artboards.add(artboard);
        // var objects = List<Core<RiveCoreContext>>(numObjects);
        for (int i = 1; i < numObjects; i++) {
          Core<CoreContext> object = readRuntimeObject(reader);
          // N.B. we add objects that don't load (null) too as we need to look
          // them up by index.
          artboard.addObject(object);
  
negative.code:           var numKeyedObjects = reader.readVarUint();
            var keyedObjects = List<KeyedObject>(numKeyedObjects);
            for (int j = 0; j < numKeyedObjects; j++) {
              var keyedObject = _readRuntimeObject<KeyedObject>(reader);
              if (keyedObject == null) {
                continue;
              }
  