Get rid of shadow form popover view controller (Swift)

Question

I am trying to create number pad in iPad using popover view controller. Everything is achieved but there is a shadow beneath the pop view. I tried to remove that shadow but nothing worked for me. Here is my code which presents pop over view in my view controller.

let vc = self.storyboard?.instantiateViewController(withIdentifier: "PopOverVC") as? PopOverVC
    vc?.modalPresentationStyle = .popover
    vc?.preferredContentSize = CGSize(width: 280, height: 425)
    vc?.delegate = self
    if let popoverPresentationController = vc?.popoverPresentationController {
        popoverPresentationController.permittedArrowDirections = [.down, .up, .right, .left]
        popoverPresentationController.sourceView = self.view
        popoverPresentationController.sourceRect = txtNumber.frame
        popoverPresentationController.delegate = self
        if let popoverController = vc {
            present(popoverController, animated: false, completion: nil)
        }
    }

Can anybody help me removing the shadow? Thanks in advance!!