def get_region(region):
    """Return the region naming used in this package.

    Parameters
    ----------
    region : str
        Regional synonym.

    Returns
    -------
    region : str
        Region either 'cena' or 'wna'.

    """
    region = region.lower()
    if region in ['cena', 'ena', 'ceus', 'eus']:
        return 'cena'
    elif region in ['wna', 'wus']:
        return 'wna'
    else:
        raise NotImplementedError('No recognized region for: %s', region)