docs: public static <T extends ViewTraverse<T>> String expandVariable(
              final MultiDataContext<T, DataContext> data,
              final T currentContext,
              final BiFunction<Integer, String, T> viewMap,
              final String step,
              final String group,
              final String key,
              final String node
      )
      {
          Integer t = null;
          if (null != step) {
              try {
                  t = Integer.parseInt(step);
              } catch (NumberFormatException e) {
                  return null;
              }
          }
          T view = viewMap.apply(t, node);
          T mergedview = view.merge(currentContext).getView();
          return data.resolve(mergedview, view, group, key, null);
      }