@Override
 public Transformer getTransformer() throws Exception {
   ObjectToJson trans = new ObjectToJson();
   trans.getSerializationMixins().put(FruitCollection.class, FruitCollectionMixin.class);
   trans.getSerializationMixins().put(Apple.class, AppleMixin.class);
   trans.getSerializationMixins().put(Orange.class, OrangeMixin.class);
   trans.setSourceClass(FruitCollection.class);
   initialiseObject(trans);
   return trans;
 }