anchor.diff:  %% extract keydata from the input
   erlang_keydata({_OkError, _Input, KeyData}) -> KeyData.
   
  +%% @doc Evaluate Javascript map functions ... if the input is ok.
   map_js(_JS, _Arg, {{error, notfound}, {Bucket, Key}, KeyData}) ->
       {ok, [{not_found,
              {Bucket, Key},
  
positive.code:         
  %% @doc Evaluate the map function.
  -spec map(riak_kv_mrc_pipe:map_query_fun(), term(), term())
           -> {ok, [term()]} | {forward_preflist, Reason :: term()}.
  map({modfun, Module, Function}, Arg, Input0) ->
      Input = erlang_input(Input0),
      KeyData = erlang_keydata(Input0),
  
negative.code:                       "   {qfun, Function :: function()}~n"
                        "   {jsanon, {Bucket :: binary(), Key :: binary()}}~n"
                        "   {jsanon, Source :: binary()}~n"
                        "   {jsfun, Name :: binary()}~n"
                        "   {strfun, Source :: string()}~n"
                        "   {strfun, {Bucket :: binary(), Key :: binary()}}~n",
                        [?MODULE])}
      end;
  validate_arg(Other) ->
  