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:     }.
  
  setup() ->
      meck:new([datastore_doc_batch, datastore_doc], [passthrough, no_history]),
      meck:expect(datastore_doc_batch, init, fun() -> #{} end),
      meck:expect(datastore_doc, save, fun(_Ctx, Key, Doc, Batch) -> {{ok, Doc}, Batch#{Key => Doc}} end),
  
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]).
  
  %%%===================================================================
  