How to get the comment of a Photo in a shared Album?

I have a shared album "iCloudSharedAlbum" using iCloud

1. How do I get comments attached to a photo?

2. How do I get the recently added comment on a photo I am observing? (Using PHPhotoLibraryChangeObserver protocol)

I have been trying with the official sample: https://developer.apple.com/library/ios/samplecode/UsingPhotosFramework/Introduction/Intro.html

I just changed a couple of lines to show shared albums (In AAPLRootListViewController awakeFromNib method)

PHFetchResult *smartAlbums = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum
                                                                          subtype:PHAssetCollectionSubtypeAlbumCloudShared options:nil];

I add a comment to the shared photo and wait for the changes to be reflected in the sample app.

-[AAPLAssetGridViewController photoLibraryDidChange:]

// self.assetsFetchResults is a list of photos I am showing. 
// There is only one photo in the list, the one being shared and the one the comment was just added
PHFetchResultChangeDetails *collectionChanges = [changeInstance changeDetailsForFetchResult:self.assetsFetchResults];

I also tried this. It is nil.

PHObjectChangeDetails *details = [changeInstance changeDetailsForObject:self.assetsFetchResults[0]]

Any help is appreciated