handler.php

См. документацию.

<?php
 
namespace Bitrix\Main\UI\Selector;
 
class Handler
{
    public const
        ENTITY_TYPE_GROUP = 'USERGROUPS';
 
    public static function getProviderByEntityType($entityType)
    {
        switch($entityType)
        {
            case self::ENTITY_TYPE_GROUP:
                $provider = new UserGroups();
                break;
            default:
                $provider = false;
        }
 
        return $provider;
    }
}