anchor.diff:  -spec read(client_key()) -> {ok, client_value()} | {fail, not_found}.
   read(Key) ->
       read_helper(Key, fun ?MODULE:rf_val/1).
  +
  +%% @doc Partially read a JSON object stored at a given key.
  +-spec fetch(client_key(), path()) ->
  +    {ok, client_value()} | {fail, not_fount} | {error, any()}.
  +fetch(Key, Path) ->
  +    read_helper(Key, get_rf_fetch_fun(Path)).
   
   %% @doc Write full JSON object to a given key.
   %% Returns:
  
positive.code:         ?SCALARIS_RECV({qread_done, _ReqId, _NextFastWriteRound, _OldWriteRound, Value},
                         case Value of
                             ?NON_EXIST_VAL -> {fail, not_found};
                             _ -> {ok, Value}
                             end
                        )
  
negative.code: %% INTERNAL HELPER
  %% %%%%%%%%%%%%%%%%
  -spec read_helper(client_key(), prbr:read_filter()) ->
      {ok, client_value()} | {fail, not_found} | {error, any()}.
  read_helper(Key, ReadFilter) ->
      rbrcseq:qread(kv_db, self(), ?RT:hash_key(Key), ?MODULE, ReadFilter),
      trace_mpath:thread_yield(),
  