Define dynamic array key with PHPStan

I have a function that looks like this

protected function getAllData(string $tableName, string $collectionKey): array
{
    // Some logic here to get records from database and store them in $records...
    $data = [
        'count' => count($records),
        $collectionKey => [],
    ];

    foreach ($records as $record) {
        $data[$collectionKey][] = [
            'name' => $record['name'],
            'value' => $record['value'],
        ];
    }

    return $data;
}

How can I define the array key $collectionKey which is passed in as a parameter`

    /**
     * @param string $tableName
     * @param string $collectionKey
     * @return array{
     *     count: int<0, max>,
     *     '?????': list<array{               <-- How?
     *         name: string,
     *         value: string,
     *     }>
     * }
     */