How to get record data or just id of a relation manager record.

 class ItemsRelationManager extends RelationManager
{
    protected static string $relationship = 'items';

    protected static ?string $recordTitleAttribute = 'id';

    public static function form(Form $form): Form
    {

//how to get the record id here
}
}

 class ItemsRelationManager extends RelationManager
{
    protected static string $relationship = 'items';

    protected static ?string $recordTitleAttribute = 'id';

    public static function form(Form $form): Form
    {

//how to get the record id here
}
}