docs: function(){
      if (!service.token) {
        return;
      }
      if(typeof(service.token.expires_in) !== 'undefined' && service.token.expires_in !== null) {
        var expires_at = new Date();
        expires_at.setSeconds(expires_at.getSeconds() + parseInt(service.token.expires_in)-60); // 60 seconds less to secure browser and response latency
        service.token.expires_at = expires_at;
      }
      else {
        service.token.expires_at = null;
      }
    }