anchor.diff:  print() ->
       gen_server:call(?MODULE, print, infinity).
   
  +%% @doc Identify trace.
  +identify(Identifier) ->
  +    gen_server:call(?MODULE, {identify, Identifier}, infinity).
  +
   %%%===================================================================
   %%% gen_server callbacks
   %%%===================================================================
  
positive.code:          terminate/2,
           code_change/3]).
  
  -record(state, {trace=[]}).
  
  %%%===================================================================
  %%% API
  
negative.code:          start_link/1,
           record/4,
           reset/0,
           identify/1,
           print/0]).
  
  %% gen_server callbacks
  