def stations_highest_rel_level(stations, N):
     """
    Function that returns the N number of most at risk stations.
    Args:
        stations (list): List of stations (MonitoringStation).
        N (int): Length of the desired list
    Returns:
        list: List of stations (MonitoringStation).
    """
     return sorted(filter(
        lambda x: x.relative_water_level() is not None,
        stations
    ),
        key=lambda x: x.relative_water_level(),
        reverse=True
    )[:N]