 <p>Because <code>NSManagedObject</code> instances returned by Core Data are lazily loaded, it is
            possible that when you access an attribute of an object, the actual row in the Amazon
            DynamoDB table has been already deleted. In this situation, the AWS Persistence
            Framework for Core Data will return an empty <code>NSManagedObject</code> (the accessor
            will return nil) and sends out
                <code>AWSPersistenceDynamoDBObjectDeletedNotification</code>