def normalize_date_fields(document, created_at='created', updated_at='updated'
    ):
    """Attempt to normalize documents to make it easier for consumers,
    particularly around sorting.
    """
    if created_at and 'created_at' not in document:
        document[u'created_at'] = document[created_at]
    if updated_at and 'updated_at' not in document:
        document[u'updated_at'] = document[updated_at]
