anchor.diff:  
       ?assertEqual(11, maps:size(Batch2)),
       DocsNums = lists:foldl(fun
  -        (#document{value = {data, Windows, _, _}}, {HeadsCountAcc, TailsCountAcc}) ->
  +        (#document{value = {histogram_tail_node, {data, Windows, _, _}}}, {HeadsCountAcc, TailsCountAcc}) ->
               ?assertEqual(50000, histogram_windows:get_size(Windows)),
               {HeadsCountAcc, TailsCountAcc + 1};
  -        (#document{value = {histogram, TimeSeries}}, {HeadsCountAcc, TailsCountAcc}) ->
  +        (#document{value = {histogram_hub, TimeSeries}}, {HeadsCountAcc, TailsCountAcc}) ->
               ?assertEqual(2, maps:size(TimeSeries)),
               MetricsMap0 = maps:get(<<"TS", 0>>, TimeSeries),
               MetricsMap1 = maps:get(<<"TS", 1>>, TimeSeries),
  
positive.code: 
      ?assertEqual(4, maps:size(Batch2)),
      DocsNums = lists:foldl(fun
          (#document{value = {data, Windows, _, _}}, {HeadsCountAcc, TailsCountAcc}) ->
              ?assertEqual(50000, histogram_windows:get_size(Windows)),
              {HeadsCountAcc, TailsCountAcc + 1};
          (#document{value = {histogram, TimeSeries}}, {HeadsCountAcc, TailsCountAcc}) ->
              [Metrics] = maps:values(TimeSeries),
              [#metrics{data = {data, Windows, _, _}}] = maps:values(Metrics),
              ?assertEqual(50000, histogram_windows:get_size(Windows)),
  
negative.code:     meck:expect(datastore_doc, delete, fun(_Ctx, Key, Batch) -> {ok, maps:remove(Key, Batch)} end).
  
  teardown(_) ->
  %%    ok.
      meck:unload([datastore_doc_batch, datastore_doc]).
  
  %%%===================================================================
  