anchor.diff:  get_sess_token(Pid) ->
       gen_server:call(Pid, get_sess_token).
   
  +-spec set_type(Type :: atom(), Pid :: pid()) -> ok.
  +set_type(_, undefined) ->
  +    ok;
  +set_type(Type, Pid) ->
  +    gen_server:call(Pid, {set_type, Type}).
  +
  +-spec get_type(Pid :: pid()) -> {ok, atom()}.
  +get_type(undefined) ->
  +    {ok, undefined};
  +get_type(Pid) ->
  +    gen_server:call(Pid, get_type).
  +
   -spec get_userid(Pid :: pid()) -> {ok, ID::binary()}.
   get_userid(Pid) ->
       gen_server:call(Pid, get_userid).
  
positive.code: -export([set_max_age/2]).
  
  -export([set_token/2]).
  
  -export([set_error/2]).
  -export([get_error/1]).
  
negative.code: -include("watts.hrl").
  -record(state, {
            id = unkonwn,
            type = undefined,
            issuer_id = undefined,
            sess_token = undefined,
            user_agent = undefined,
  