     }
     
     override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
-        let maybeCell = collectionView.dequeueReusableCell(withReuseIdentifier: cellReuseIdentifier, for: indexPath)
+        let maybeCell = collectionView.dequeueReusableCell(withReuseIdentifier: ExploreCardCollectionViewCell.identifier, for: indexPath)
         guard let cell = maybeCell as? ExploreCardCollectionViewCell else {
             return maybeCell
         }

    lazy var layoutCache: ColumnarCollectionViewControllerLayoutCache = {
       return ColumnarCollectionViewControllerLayoutCache()
    }()
    
    @objc var dataStore: MWKDataStore! {
        didSet {

    
    override func collectionView(_ collectionView: UICollectionView, estimatedHeightForHeaderInSection section: Int, forColumnWidth columnWidth: CGFloat) -> WMFLayoutEstimate {
        var estimate = WMFLayoutEstimate(precalculated: false, height: 100)
        guard let header = layoutManager.placeholder(forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: ExploreHeaderCollectionReusableView.identifier) as? ExploreHeaderCollectionReusableView else {
            return estimate
        }
        header.prepareForReuse()
