def _get_period(member):
    """Get period for which an artist is/was part of a group, orchestra or choir.

    Args:
        member (Dict): Dictionary containing the artist information.

    Returns:
        Tuple containing the begin and end year during which an artist was part of
        a group.
    """
    begin_date = member.get('begin-year', '')
    end_date = member.get('end-year', '')

    if not (begin_date or end_date):
        return None
    return str(begin_date), str(end_date)