def get_undone(single_list):
    """
    Returns the number of undone tasks in a list.
    Takes:
        - a single todo list
    Returns:
        the number of undone tasks from that list
    """
    undone = 0
    for task_id in single_list:
        if not single_list[task_id][1]:
            undone += 1
    return undone
