Transforms atomic system information into well-formatted labels.

    Parameters
    ----------
    df : Pandas DataFrame.

    Returns
    -------
    labels : list of system labels.

def auto_labels(df):
    """Transforms atomic system information into well-formatted labels.

    Parameters
    ----------
    df : Pandas DataFrame.

    Returns
    -------
    labels : list of system labels.
    """
    systems = list(df.system)
    facets = list(df.facet)
    systems_labels = [w.replace('_', '\ ') for w in systems]
    systems_labels = [sub(w) for w in systems_labels]
    systems_labels = [w.replace('}$$_{', '') for w in systems_labels]
    systems_labels = [w.replace('$', '') for w in systems_labels]
    systems_labels = ['$' + w + '$' for w in systems_labels]

    facets_label = [w.replace('_', '\ ') for w in facets]
    facets_label = ['(' + w + ')' for w in facets_label]

    labels = []
    for i, sys in enumerate(systems_labels):
        labels.append(sys + facets_label[i])
    # labels = list(set(labels))
    return(labels)