class FieldOptionTranslation

class FieldOptionTranslation extends ProcessPluginBase {
    
    /**
     * {@inheritdoc}
     *
     * Get the field default/mapped settings.
     */
    public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
        list($type, $data) = $value;
        $data = unserialize($data);
        $allowed_values = '';
        $translation_key = $row->getSourceProperty('property');
        $i = 0;
        if (isset($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])) {
                        $allowed_values = [
                            'label' => $row->getSourceProperty('translation'),
                        ];
                        break;
                    }
                    break;
                default:
            }
        }
        return [
            "settings.allowed_values.{$translation_key}",
            $allowed_values,
        ];
    }

}