How do you change layoutAttributes in a collectionView

I have a UICollectionView and I want to change the layoutAttributes of my collectionView.

I am calling this function:

override func apply(_ layoutAttributes: UICollectionViewLayoutAttributes) {

        print("Layout has been changed lit fool.")

        let targetSize = CGSize(width: 10, height: 40)

        layoutAttributes.frame.size = contentView.systemLayoutSizeFitting(targetSize, withHorizontalFittingPriority: .required, verticalFittingPriority: .fittingSizeLevel)

    }

For some reason my layoutAttributes are not being effected by this code. No matter what variable I change my targetSize to, the collectionView size stays the same. The print statement is running, so I know that this function is getting called correctly, its just the layoutAttributes don't change.

How do I get my layoutAttributes to change from this function?