anchor.diff:              maybe_tombstone(maybe_resolve(PKey, Existing, ResolveMethod), Default)
       end.
   
  -%% @spec same as fold(Fun, Acc0, FullPrefix, []).
  +%% @doc same as fold(Fun, Acc0, FullPrefix, []).
   -spec fold(fun(({metadata_key(),
                    [metadata_value() | metadata_tombstone()] |
                    metadata_value() | metadata_tombstone()}, any()) -> any()),
  
positive.code: 
  fold_it(Fun, Acc, It) ->
      case itr_done(It) of
          true -> Acc;
          false ->
              Next = Fun(itr_key_values(It), Acc),
              fold_it(Fun, Next, itr_next(It))
  
negative.code: fold(Fun, Acc0, FullPrefix) ->
      fold(Fun, Acc0, FullPrefix, []).
  
  %% @doc Fold over all keys and values stored under a given prefix/subprefix. Available
  %% options are the same as those provided to iterator/2.
  -spec fold(fun(({metadata_key(),
                   [metadata_value() | metadata_tombstone()] |
  