if query.hasCachedResult{
        query.cachePolicy = .cacheThenNetwork
        } else{
        query.cachePolicy = .networkOnly
        }

self.messages.removeAll()
self.users.removeAll()

override func collectionView(_ collectionView: JSQMessagesCollectionView!,
    messageDataForItemAt indexPath: IndexPath!) -> JSQMessageData! {

    return self.messages[indexPath.item]
}