anchor.diff:  
       %% TODO check length(KeySig) == 1
   
  -    [$a, ${, KeySig, ValueSig, $}];
  +    %% TODO use reverse?
  +    "a{" ++ KeySig ++ ValueSig ++ "}";
   marshal_signature([]) ->
       "";
   marshal_signature([Type|R]) ->
  
positive.code: marshal_signature(signature) ->
      "g";
  marshal_signature({array, Type}) ->
      [$a, marshal_signature(Type)];
  marshal_signature({struct, SubTypes}) ->
      [$(, marshal_struct_signature(SubTypes, []), $)];
  marshal_signature(variant) ->
      "v";
  marshal_signature({dict, KeyType, ValueType}) ->
  
negative.code: marshal_struct_signature([], Res) ->
      Res;
  marshal_struct_signature([SubType|R], Res) ->
      marshal_struct_signature(R, Res ++ marshal_signature(SubType)).
  
  %% unmarshal(Type, Binary) ->
  
  