FBAdViewControllerProxy is a final class and cannot be subclassed. FBAdViewControllerProxy

I Integrated FB audience network and when I run the app it crushes and I get this exception:

Terminating app due to uncaught exception 'FBFinalClassViolationException', reason: 'FBAdViewControllerProxy is a final class and cannot be subclassed. FBAdViewControllerProxy'
terminating with uncaught exception of type NSException
CoreSimulator 732.18.6 - Device: iPhone 11 

And it's working fine when I switch to Android and I tried to edit Podfile to:

target 'UnityFramework' do
  pod 'FBAudienceNetwork', '~> 6.2.0'
end

and I even deleted everything in the Podfile and build then clean but it seems it has no effect. maybe I am missing something, can someone please help?

The Solution was to change podfile to:

target 'Unity-iPhone Tests' do
end
target 'UnityFramework' do
  pod 'FBAudienceNetwork', '~> 6.2.0'
end

and then open the project in terminal and run : pod install