Terminating app due to uncaught exception 'NSInvalidArgumentException' Unknown layout attribute'

Question

I am trying to give vertical space constraint programatically for Admob native ads compenents by using NSLayoutConstraint.

I assigned nativeAdView in the ListTileNativeAdFactory class.

(I used this guide : https://codelabs.developers.google.com/codelabs/admob-inline-ads-in-flutter#7)

let nativeAdView = nibView as! GADNativeAdView 

In fact I can give height constraint without a problem.

This code works without a problem:(It gives height constraint to nativeAdView.mediaView)

   if let mediaView = nativeAdView.mediaView{
        NSLayoutConstraint(
            item: mediaView,
            attribute: NSLayoutConstraint.Attribute.height,
            relatedBy: NSLayoutConstraint.Relation.equal,
            toItem: nil,
            attribute: NSLayoutConstraint.Attribute.notAnAttribute,
            multiplier: 1,
            constant: 120).isActive = true
        }

On the other hand, If I try to give vertical space constraint(top) with this code:

   if let mediaView = nativeAdView.mediaView, let calltoActionView = nativeAdView.callToActionView{
            NSLayoutConstraint(
                item: mediaView,
                attribute: NSLayoutConstraint.Attribute.top,
                relatedBy: NSLayoutConstraint.Relation.equal,
                toItem: calltoActionView,
                attribute: NSLayoutConstraint.Attribute.notAnAttribute,
                multiplier: 1,
                constant: 15).isActive = true
            }

It gives Unknown layout attribute error.

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'NSLayoutConstraint for <GADMediaView: 0x11c0552e0; frame = (35 369.5; 250 150); autoresize = RM+BM; layer = <CALayer: 0x2801e2f00>>: Unknown layout attribute' terminating with uncaught exception of type NSException

I'm using Google's official NativeAdView file.

github.com/googleads/googleads-mobile-flutter/blob/master/packages/google_mobile_ads/example/ios/Runner/NativeAdView.xib

How can I solve this problem?