anchor.diff:                  {PartIdx,
                    {
                      safe_hd(
  -                     partition_to_preflist(PartIdx, NVal, Offset, UpNodes)),
  +                     partition_to_preflist(PartIdx, NVal, Offset, UpNodes, CHBin)),
                      []
                    }
                   }
  
positive.code:     %% new value to `riak_core_apl' as a document index.
      DocIdx = convert(SubpID, subpartition_index) - RingIndexInc,
      PrefList =
          docidx_to_preflist(DocIdx, NVal, Offset, UpNodes),
      singular_preflist_to_chunk(PrefList, SubpID).
  
  singular_preflist_to_chunk([], _SubpID) ->
  
negative.code:                           %% components of the coverage plan
                            {PartID, SubpID,
                             check_pvc(
                               docidx_to_preflist(SubpIndex, NVal, Offset, UpNodes, CHBin),
                               PVC, VNodeTarget)}
                    end,
                    lists:seq(0, Count - 1)),
  