'Returns a list of image IDs that are in the queue. The
list should be sorted by the time the image ID was inserted
into the queue.'

def get_queued_images(self):

    files = [f for f in get_all_regular_files(self.queue_dir)]
    items = []
    for path in files:
        mtime = os.path.getmtime(path)
        items.append((mtime, os.path.basename(path)))
    items.sort()
    return [image_id for (modtime, image_id) in items]
