def get_date_range(dates):
    """ Gets the date range from a set of dates

    Args:
        dates: set of dates (strings)

    Returns:
        date range as a string. Either a single date or
        [earliest date] - [latest date]
    """
    dates = filter(lambda x: x != "", dates)
    sorted_dates_list = sorted(list(dates))
    if not sorted_dates_list:
        return ""
    date_range = sorted_dates_list[0]
    if len(sorted_dates_list) > 1:
        date_range = f'{sorted_dates_list[0]} – {sorted_dates_list[-1]}'
    return date_range