anchor.diff:              Ref
       end,
       gen_server:call(Pid, {get, Start, End}).
  +
  +keys() ->
  +    Root = [code:priv_dir(yasa), "/storage/*"],
  +    lists:flatten([walk_directory_tree(Root)]).
   
   %%===================================================================
   %% Internal
  
positive.code:     {ok, Pid} = Reply = yasa_rrd_sup:start_child(Type, Key),
      yasa_pid_store:insert(Key, Pid),
      Reply.
  
negative.code: -module(yasa).
  -export([
      counter/2,
      gauge/2,
      get/3,
      walk_directory_tree/1,
      keys/0]).
  
  %%===================================================================
  %% Public API
  