public function gettotalQuantity()
 {
     $inventorycountReplenish = inventorycount::where('product_id', $this->id)->where('type', 'replenish')->sum('amount');
     $inventorycountWithdraw = inventorycount::where('product_id', $this->id)->where('type', 'withdraw')->sum('amount');
     return $inventorycountReplenish - $inventorycountWithdraw;
 }