Laravel excel library(Maatwebsite) : How to create a drop down with multiple select for Export

I'm using Laravel Excel to export excel with larvel. I need a dropdown with multiple select.

use App\MyModel;
use Maatwebsite\Excel\Concerns\FromArray;
use Maatwebsite\Excel\Concerns\WithHeadings;

class MyModelExport implements FromArray, WithHeadings
{
    public $rowCount = 0;
    public function array(): array
    {
        $branches = MyModel::get([
            "title",
            "ranks",
        ]);

        $data = [];
        

        foreach ($items $key => $item) {

            $data[$key]['title'] = $item->title;
            $data[$key]['ranks'] = $item->ranks;
        }

        $this->rowCount = count($data);
        return $data;
    }

    public function registerEvents(): array {
        
        return [
            AfterSheet::class => function(AfterSheet $event) {
                /** @var Sheet $sheet */
                $sheet = $event->sheet;

                /**
                 * validation for bulkuploadsheet
                 */
                
                for($i=2; $i<=$this->rowCount+1; $i++){
                    $sheet->setCellValue('B'.$i, $sheet->getCell('B'.$i)->getValue());
                    $configs = "dis1, dis 2, dis 3";
                    $objValidation = $sheet->getCell('B'.$i)->getDataValidation();
                    $objValidation->setType(DataValidation::TYPE_LIST);
                    $objValidation->setErrorStyle(DataValidation::STYLE_INFORMATION);
                    $objValidation->setAllowBlank(false);
                    $objValidation->setShowInputMessage(true);
                    $objValidation->setShowErrorMessage(true);
                    $objValidation->setShowDropDown(true);
                    $objValidation->setErrorTitle('Input error');
                    $objValidation->setError('Value is not in list.');
                    $objValidation->setPromptTitle('Pick from list');
                    $objValidation->setPrompt('Please pick a rank from the drop-down list.');
                    $objValidation->setFormula1('"' . $configs . '"');
                }
            },
        ];
    }

    public function headings(): array
    {
        return [
            'Title',
            'Ranks'
        ];
    }
}

This code gives a dropdown. But what I need a dropdown with multiple selects. Simply I need to select multiple ranks in one cell.

via Chebli Mohamed