anchor.diff:  %% ====================================================================
   -export([add_value/3,
   	 add_values/2,
  +	 convert_undefined/1,
   	 decode/1, 
   	 encode/1, 
   	 field_value_exists/3, 
  
positive.code: %% @end
  -spec add_values(Json::json(), [{Field::field(),Value::json_input_value()}]) -> json_output_value().
  add_values(Json, FieldsAndValues) ->
      Fun = fun({Attr, Value}, Acc) -> add_value(Acc, Attr, Value) end,
      lists:foldl(Fun, Json, FieldsAndValues).
  
  %% @doc 
  %% Decodes a json object into mochijson format.
  %%
  
negative.code: %% @hidden
  %% Function: parse_value/1
  %% @end
  parse_value(undefined) ->
      <<>>;
  parse_value([]) ->
      [];
  parse_value(Value) when is_tuple(Value)->
      erlson:from_json_term(Value);
  parse_value(Value) when is_list(Value) ->
  