Permissionmanager error i no clue why

My code

PHP:

PlayerJoiNEvent
$attachment = $player->addAttachment( $this->plugin );

$this->plugin->attachments[$uuid->toString()] = $attachment;
call setPermissions
}
setPermissions
$permissions = ['gu.fa', 'kake.ap'];
           $attachment = $this->attachments[$uuid];
            $attachment->clearPermissions();

            $attachment->setPermissions($permissions);

and I get error

Code:

[23:07:26] [Server thread/CRITICAL]: TypeError: "Argument 1 passed to pocketmine\permission\PermissionManager::getPermission() must be of the type string, int given, called in phar://D:/PC/Desktop/mc/PocketMine-MP/PocketMine-MP.phar/src/pocketmine/permission/Permis
sibleBase.php on line 155" (EXCEPTION) in "src/pocketmine/permission/PermissionManager" at line 58

I'm never even used PermissionManager::getPermission() .. i think it's with the $attachment->setPermissions($permissions); I don't know.