Stevebauman\Inventory\Traits\InventoryTransactionTrait::setQuantityAttribute PHP Method

    public function setQuantityAttribute($quantity)
    {
        if (!$this->isPositive($quantity)) {
            $message = Lang::get('inventory::exceptions.InvalidQuantityException');
            throw new InvalidQuantityException($message);
        }
        $this->attributes['quantity'] = $quantity;
    }