@Override
    public Map<Class<?>, EventProducer> findAllProducers(Object listener) {
      return HandlerFinder.ANNOTATED.findAllProducers(listener);
    }
Delegates to {@code HandlerFinder.ANNOTATED}, then sorts results by {@code EventHandler#toString}
otto/src/test/java/com/squareup/otto/UnregisteringHandlerTest.java