anchor.diff:      gen_server:cast(?MODULE, {increment, Key, Amount}).
   
   
  -append(Key, Value) ->
  -    gen_server:cast(?MODULE, {append, Key, Value}).
  +record(Key, Value) ->
  +    gen_server:cast(?MODULE, {record, Key, Value}).
   
   
   %%%===================================================================
  
positive.code: -export([start_link/0,
           increment/1,
           increment/2,
           append/2]).
  
  %% gen_server callbacks
  -export([init/1,
  
negative.code: increment_metrics(_Key, _Amount, Map) -> Map.
  
  
  record_metrics(Key, Value, Map) when is_number(Value) ->
      Update = fun(Values) when is_list(Values) -> [Value | Values];
                  (Values) -> Values end,
      maps:update_with(Key, Update, [Value], Map);
  record_metrics(_Key, _Value, Map) -> Map.
  
  
  %%%===================================================================
  