// MARK: - Expanding/Collapsing Logic

func expand(in collectionView: UICollectionView) {
    initialFrame = self.frame
    initialCornerRadius = self.contentView.layer.cornerRadius

    self.contentView.layer.cornerRadius = 0
    self.frame = CGRect(x: 0, y: collectionView.contentOffset.y, width: collectionView.frame.width, height: collectionView.frame.height)

    layoutIfNeeded()
}

func collapse() {
    self.contentView.layer.cornerRadius = initialCornerRadius ?? self.contentView.layer.cornerRadius
    self.frame = initialFrame ?? self.frame

    initialFrame = nil
    initialCornerRadius = nil

    layoutIfNeeded()
}