Laravel | Laravel-excelで複数行のヘッダー出力方法

<?php

namespace App\Exports;

use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
use Maatwebsite\Excel\Concerns\Exportable;
use Maatwebsite\Excel\Concerns\FromCollection;
use Maatwebsite\Excel\Concerns\WithTitle;
use Maatwebsite\Excel\Concerns\WithHeadingRow;
use Maatwebsite\Excel\Concerns\WithMapping;
use Maatwebsite\Excel\Concerns\WithColumnFormatting;
use PhpOffice\PhpSpreadsheet\Shared\Date;
use PhpOffice\PhpSpreadsheet\Style\NumberFormat;
use Maatwebsite\Excel\Concerns\WithCustomStartCell;
use Carbon\Carbon;

/**
 *
 * @author nextk
 *
 */
class ExportAccountSample implements FromCollection, WithColumnFormatting, WithMapping, WithCustomStartCell, WithTitle
{
    use Exportable;

    /**
     *
     * @param unknown $data
     * @return array
     */
    public function map($data): array
    {
       return $data;
    }


    /**
     *
     * @return string
     */
    public function startCell(): string
    {
        return 'A1';
    }

    /**
     *
     * @return string
     */
    public function title(): string{
        return 'sample';
    }

    /**
    * @param Collection $collection
    */
    public function collection()
    {
        return collect(
            ['1行目'],
            ['2行目'],
            [
                '3行目：1列目',
                '3行目：2列目',
                '3行目：3列目',
            ]
        );
    }
}

<?php

namespace App\Exports;

use Illuminate\Support\Collection;

use Illuminate\Support\Facades\DB;

use Maatwebsite\Excel\Concerns\Exportable;

use Maatwebsite\Excel\Concerns\FromCollection;

use Maatwebsite\Excel\Concerns\WithTitle;

use Maatwebsite\Excel\Concerns\WithHeadingRow;

use Maatwebsite\Excel\Concerns\WithMapping;

use Maatwebsite\Excel\Concerns\WithColumnFormatting;

use PhpOffice\PhpSpreadsheet\Shared\Date;

use PhpOffice\PhpSpreadsheet\Style\NumberFormat;

use Maatwebsite\Excel\Concerns\WithCustomStartCell;

use Carbon\Carbon;

/**

* @author nextk

class ExportAccountSample implements FromCollection, WithColumnFormatting, WithMapping, WithCustomStartCell, WithTitle

{

use Exportable;

/**

* @param unknown $data

* @return array

public function map($data): array

{

return $data;

}

/**

* @return string

public function startCell(): string

{

return 'A1';

}

/**

* @return string

public function title(): string{

return 'sample';

}

/**

* @param Collection $collection

public function collection()

{

return collect(

['1行目'],

['2行目'],

[

'3行目：1列目',

'3行目：2列目',

'3行目：3列目',

]

);

}

400 Bad Request