anchor.diff:  change_list(TableId, DirtyCnt, DirtyTop, DirtyBot) ->
       [tuple_to_list(R) || R <- change_tuples(TableId, DirtyCnt, DirtyTop, DirtyBot)].
   
  --spec write_subscription(binary(), binary(), #state{}) -> ok | {error, term()}.
  +-spec write_subscription(binary(), binary(), #state{}) -> ok | {error, term()}.
   write_subscription(Topic, Key, #state{ctx = #ctx{update_cursor_prepare_fun = Ucpf, update_cursor_execute_fun = Ucef}}) ->
       %% TODO: Read and update maybe is needed for multiple topic subscription.
       SubsKey = imem_json:encode([<<"register">>, <<"focus">>, [atom_to_binary(node(), utf8), list_to_binary(pid_to_list(self()))]]),
  
positive.code:     state_functions.
  
  %% --------------------------------------------------------------------
  %% Func: handle_call/4 handling sync "send_all_state_event""
  %% Returns: {next_state, NextSN, NextStateData}            |
  %%          {next_state, NextSN, NextStateData, Reply}   |
  %%          {stop, Reason, NewStateData}                          |
  
negative.code:                 _ChangedKeys -> ok
              end;
          {_, Error} -> {error, Error}
      end.