anchor.diff:      toke_drv:delete(DB, ?IN(Key)),
       State.
   
  -%% @doc Returns the name of the DB specified in new/1.
  +%% @doc Returns the name of the DB specified in @see new/1.
   -spec get_name(DB::db()) -> nonempty_string().
   get_name({_DB, FileName}) ->
       FileName.
  
positive.code:                                          AccIn
                                   end
                           end, [], DB),
      lists:foldl(Fun, Acc, Data).
  
  %% @doc foldl iterates over DB and applies Fun(Entry, AccIn) to every element
  %%      encountered in Interval. On the first call AccIn == Acc0. The iteration
  %%      stops as soon as MaxNum elements have been encountered.
  -spec foldl(DB::db(), Fun::fun((Entry::entry(), AccIn::A) -> AccOut::A), Acc0::A,
                                 Intervall::db_backend_beh:interval(), MaxNum::non_neg_integer()) -> Acc1::A.
  foldl({DB, _FileName}, Fun, Acc, Interval, MaxNum) ->
  
negative.code:                                          AccIn
                                   end
                           end, [], DB),
      %% see HINT in foldl/3
      lists:foldr(Fun, Acc, Data).
  
  %% @doc foldr iterates over DB and applies Fun(Entry, AccIn) to every element
  %%      encountered in Interval. On the first call AccIn == Acc0. The iteration
  %%      stops as soon as MaxNum elements have been encountered.
  %%      Returns a potentially larger-than-memory dataset. Use with care.
  -spec foldr(DB::db(), Fun::fun((Entry::entry(), AccIn::A) -> AccOut::A), Acc0::A,
                                 Intervall::db_backend_beh:interval(), MaxNum::non_neg_integer()) -> Acc1::A.
  foldr({DB, _FileName}, Fun, Acc, Interval, MaxNum) ->
  