def METHOD_NAME(tasks, engine_number_map):
    """Plot usage stats"""
    plt.figure(figsize=(8, 8))
    for engine_uuid, task_list in tasks.items():
        engine_number = engine_number_map[engine_uuid]
        number_list = [engine_number] * len(task_list)
        start_list = [task['started'] for task in task_list]
        completed_list = [task['completed'] for task in task_list]
        plt.plot(
            [number_list, number_list],
            [start_list, completed_list], linewidth=10,
            solid_capstyle="butt")
    plt.xlim(min(engine_number_map.values()) - 1,
             max(engine_number_map.values()) + 1)
    plt.xlabel('Compute engine number')
    plt.ylabel('Compute time')
    idle_time, idle_perc = calculate_unused_compute(tasks)
    plt.title(
        'Cumulative idle time: %s, perc: %.2f %%' %
        (idle_time, idle_perc))