anchor.diff:  %% @doc Saves arbitrary tuple Entry in DB DBName and returns the new DB.
   %%      The key is expected to be the first element of Entry.
   -spec put(DB::db(), Entry::entry()) -> db().
  -put({DB, FileName}, Entry) ->
  +put({DB, _FileName} = State, Entry) ->
       toke_drv:insert(DB, ?IN(element(1, Entry)), ?IN(Entry)),
  -    {DB, FileName}.
  +    State.
   
   %% @doc Returns the entry that corresponds to Key or {} if no such tuple exists.
   -spec get(DB::db(), Key::key()) -> entry() | {}.
  
positive.code: -spec foldl(DB::db(), Fun::fun((Entry::entry(), AccIn::A) -> AccOut::A), Acc0::A,
                                 Intervall::backend_beh:interval(), MaxNum::non_neg_integer()) -> Acc1::A.
  foldl({DB, _FileName}, Fun, Acc, Interval, MaxNum) ->
      {_Left, Data} = toke_drv:fold(fun(_Key, Entry, {Max, AccIn}) ->
                                   DeCoded = ?OUT(Entry),
                                   case is_in(Interval, element(1, DeCoded))
                                        andalso Max > 0 of
                                       true ->
                                           {Max - 1, [DeCoded | AccIn]};
                                       _ ->
                                           {Max, AccIn}
                                   end
                           end, {MaxNum, []}, DB),
      lists:foldl(Fun, Acc, Data).
  
  %% @doc Is equivalent to ets:foldr(Fun, Acc0, DB).
  
negative.code:         ok ->
              case toke_drv:open(DB, FileName, TokeOptions) of
                  ok -> {DB, FileName};
                  Error2 ->
                      log:log(error, "[ Node ~w:db_toke ] ~.0p", [self(), Error2]),
                      erlang:error({toke_failed, Error2})
              end;
          Error1 ->
  