anchor.diff:  
   %% API
   -export([start_link/0, start_link/1]).
  --export([start/0, start/1, stop/0]).
  +-export([start/0, stop/0]).
   
   %% gen_server callbacks
   -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
  
positive.code: 
  unsubscribe(Ref) ->
      gen_server:call(?SERVER, {unsubscribe,Ref}).
  
  get_root(What,Fam) ->
      get(What,Fam,[root,match,request],[]).
  
negative.code: -export([i/0, list/1]).
  -export([subscribe/1, subscribe/2, subscribe/3]).
  -export([unsubscribe/1]).
  -export([invalidate/2]).
  -export([get_root/2, get_match/3, get/4]).
  
  -include_lib("lager/include/log.hrl").
  