code: public static It<Object> findVis(VisualizerContext context) {
      return new StackedIter<>(context.getHierarchy().iterAll(), context.getVisHierarchy());
    }
docs: Filtered iteration over a stacked hierarchy.
  
  This is really messy because the visualization hierarchy is typed Object.
  
  @param context Visualization context
  @return Iterator of results.