code: @Override
      protected EnumSet<C.Feature> initFeatures() {
          EnumSet<C.Feature> fs = (data instanceof C.List) ?
                  ((C.List<T>)data).features()
                  : EnumSet.of(C.Feature.LIMITED, C.Feature.ORDERED);
          if (data instanceof RandomAccess) {
              fs.add(C.Feature.RANDOM_ACCESS);
          }
          return fs;
      }
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