anchor.diff:  %% ```
   %% > Json = "{\"attr1\":\"value1\"}".
   %% > Field = "attr2".
  -%% > Value = "value2".
  +%% > Value = <<"value2">>.
   %% > lib_json:add_value(Json, Field, Value).
   %% "{\"attr1\":\"value1\", \"attr2\":\"value2\"}"
   %% '''
  
positive.code: 	 replace_field/3,
  	 rm_field/2,
  	 set_attr/2,
  	 to_string/1]).
  %% ====================================================================
  %% Specialized functions - Exports
  
negative.code: %% API functions - Exports
  %% ====================================================================
  -export([add_value/3,
  	 add_values/2,
  	 decode/1, 
  	 encode/1, 
  	 field_value_exists/3, 
  