code: function (id, fields, done, headers, config) {
          if (!_.isNumber(parseInt(id, 10))) {
            return done(new Error('id must be specified.'));
          }
          if (!_.isObject(fields)) {
            return done(new Error('An fields object must be provided.'));
          }
          this._request(['folders', id], 'PUT', done, null, fields, null, headers, null, config);
        }
docs: Fields to set for {@link Connection#updateFolder}.
  @external FieldsUpdateFolder
  @see {@link https://developers.box.com/docs/#folders-update-information-about-a-folder}
   
  Used to update information about the folder. To move a folder, update the ID of its parent.
  To enable an email address that can be used to upload files to this folder, update the
  {@linkcode fields.folder_upload_email} attribute. An optional {@linkcode header[If-Match]}
  header can be included to ensure that client only updates the folder if it knows about
  the latest version.
  @summary Update Information About a Folder.
  @see {@link https://developers.box.com/docs/#folders-update-information-about-a-folder}
  @param {number} id - The folder's ID.
  @param {external:FieldsUpdateFolder} fields - The fields to update.
  @param {requestCallback} done - The callback to invoke (with possible errors) when the request returns.
  @param {?RequestHeaders} [headers] - Additional headers.
  @param {?RequestConfig} [config] - Configure the request behaviour.