PluginExample.php

<?php

declare (strict_types=1);
namespace Drupal\plugin_test\Plugin\Attribute;

use Drupal\Component\Plugin\Attribute\Plugin;

/**
 * Defines a custom PluginExample attribute.
 */
class PluginExample extends Plugin {
    
    /**
     * Constructs a PluginExample attribute.
     *
     * @param string $id
     *   The plugin ID.
     * @param string $custom
     *   Some other sample plugin metadata.
     */
    public function __construct(string $id, ?string $custom = NULL) {
    }

}