Paywall on purchase start callback

Hi, I’m using Paywalls feature in my SwiftUI App. I want to disable Paywall interactions while purchase is in progress, is there onPurchaseStart callback or something? here is my current implementation:

                .sheet(isPresented: $userViewModel.displayPayWall) {
                    PaywallView(displayCloseButton: true)
                        .onPurchaseCompleted({ userInfo in
                            print("completed")
                            userViewModel.isPurchasing = false
                            userViewModel.isSubscriptionActive = userInfo.entitlements["pro"]?.isActive ?? false
                        })
                        .interactiveDismissDisabled(userViewModel.isPurchasing)
                }