Compute season (DJF, MAM, JJA, SON) from month ordinal

def _season_from_months(months):
    """Compute season (DJF, MAM, JJA, SON) from month ordinal
    """
    # TODO: Move "season" accessor upstream into pandas
    seasons = np.array(['DJF', 'MAM', 'JJA', 'SON'])
    months = np.asarray(months)
    return seasons[(months // 3) % 4]