Change default title of right bar button in PHPickerViewController

Question

I'm implementing the new iOS 14 image picker PHPickerViewController. By default the right bar button has the title "Add". I want to change this to "Stamp". I tried the code below but it did not work. Does anyone know how to change the right bar button title for PHPickerViewController?

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let picker = PHPickerViewController(configuration: pickerConfiguartion)
picker.navigationController?.navigationItem.rightBarButtonItem?.title = "Stamp"