TargetBundle.php

<?php

namespace Drupal\taxonomy\Plugin\migrate\process;

use Drupal\migrate\MigrateExecutableInterface;
use Drupal\migrate\ProcessPluginBase;
use Drupal\migrate\Row;

/**
 * Converts a Drupal 6 vocabulary ID to a target bundle array.
 *
 * @MigrateProcessPlugin(
 *   id = "target_bundle"
 * )
 */
class TargetBundle extends ProcessPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
        $target_bundle = [];
        $vid = $row->get('@_vid');
        $target_bundle[$vid] = $vid;
        return $target_bundle;
    }

}