def extract_extra_labels(metadata_dict):
    """Return the 'extra_labels' labels from metadata_dict, as a list."""
    labels = metadata_dict.get('extra_labels', None)
    if labels:
        extra_labels = labels.split(', ')
        extra_labels = [label.lower().encode('utf-8')
                        for label in extra_labels]
    else:
        extra_labels = labels
    return extra_labels