code: function(subscription_id) {
      var params = {
        client_id:     this._credentials.client_id,
        client_secret: this._credentials.client_secret
      };
      if (subscription_id==='users') {
        params.object = 'user';
      } else if (subscription_id==='all') {
        params.object = 'all';
      } else {
        params.id = subscription_id;
      }
      return params;
    }
docs: Generate request parameters for unsubscribing