def get_class_names_from_class_mapping(class_mapping):
    """
    Parameters
    ----------
    class_mapping : list(list), optional
        class_mapping as it represented in deployment_document.json:
        [["GALAXY", 0], ["QSO", 1], ["STAR", 2]]
    Returns
    -------
    classes, sorted list of class labels
    """
    if not class_mapping:
        return None
    return [kv[0] for kv in sorted(class_mapping, key=lambda v: v[1])]