Issue #3308593 by danquah: Add _deconfig config entry at the end of the config

   */

  protected function implode($hideSpec, $data, $lax) {

    if ($hideSpec) {

      $data = [($lax ? '@' : '') . self::KEY => $hideSpec] + $data;

      // Add our hide spec to the end of the config-data.

      // Ideally we would want the entry mixed in with the other config

      // properties ideally sorted by key name. But, as castValue() in cores

      // StorableConfigBase will sort all Mapping config properties according to

      // its dataDefinition and leave all remaining config-entires in the end of

      // the config array.

      // So, we tag our entry to the end of the existing config to match this.

      $data += [($lax ? '@' : '') . self::KEY => $hideSpec];

    }

    return $data;