anchor.diff:  
   -endif. % SLF_COMMENT
   
  -%% @doc Fold over all the buckets.
  --spec fold_buckets(riak_kv_backend:fold_buckets_fun(),
  -                   any(),
  -                   [],
  -                   state()) -> {ok, any()} | {async, fun()} | {error, term()}.
  -fold_buckets(_FoldBucketsFun, Acc, _Opts, _S) ->
  -    Acc.                                        % lazy!
  -
   %% @doc Fold over all the keys for one or all buckets.
   -spec fold_keys(riak_kv_backend:fold_keys_fun(),
                   any(),
  
positive.code: %%     Config = [{riak_kv_fs_backend_root, "test/fs-backend"}],
  %%     ?assertCmd("rm -rf test/fs-backend"),
  %%     ?assertEqual(true, backend_eqc:test(?MODULE, false, Config, Cleanup)).
  -endif. % EQC
  -endif. % TEST
  
negative.code: is_empty(State) -> ?MODULE:list(State) =:= [].
  
  fold(State, Fun0, Acc) ->
      Fun = fun(BKey, AccIn) ->
                    case ?MODULE:get(State, BKey) of
                        {ok, Bin} ->
                            Fun0(BKey, Bin, AccIn);
  