How can I hide "Groups" and cancel button in CNContactPickerViewController?

Question

Im using a CNContactPickerViewController and I want to hide the cancel and the group buttons I tried contactPickerViewController.navigationItem.leftBarButtonItem = nil and

contactPickerViewController.navigationItem.hidesBackButton = true

but that doesnt work.. Here my code to create the controller

let contactPickerViewController = CNContactPickerViewController()

    contactPickerViewController.predicateForEnablingContact = NSPredicate(format: "phoneNumbers.@count > 0",
        argumentArray: nil)

    contactPickerViewController.delegate = self
    contactPickerViewController.navigationItem.leftBarButtonItem = nil
    contactPickerViewController.navigationItem.hidesBackButton = true

    presentViewController(contactPickerViewController, animated: true, completion: nil)

Help anyone? Thanks