class FieldOptionTranslation

class FieldOptionTranslation extends ProcessPluginBase {
  
  /**
   * {@inheritdoc}
   *
   * Get the field default/mapped settings.
   */
  public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
    [
      $type,
      $data,
    ] = $value;
    $data = unserialize($data);
    $new_allowed_values = '';
    $translation_key = $row->getSourceProperty('property');
    if (isset($data['settings']['allowed_values'])) {
      $allowed_values = $data['settings']['allowed_values'];
      switch ($type) {
        case 'list_string':
        case 'list_integer':
        case 'list_float':
        case 'list_text':
          if (isset($allowed_values[$translation_key])) {
            $new_allowed_values = [
              'label' => $row->getSourceProperty('translation'),
            ];
            $translation_key = array_search($translation_key, array_keys($allowed_values));
            break;

          }
          break;

        default:
          $new_allowed_values = $allowed_values;
      }
    }
    return [
      "settings.allowed_values.{$translation_key}",
      $new_allowed_values,
    ];
  }

}