def get_video_json(video):
    """
    helper function: given an image, return the json to pass back to the
    image chooser panel
    """

    return json.dumps({
        'id': video.id,
        'edit_link': reverse('wagtailvideos:edit', args=(video.id,)),
        'title': video.title,
        'preview': {
            'url': video.thumbnail.url if video.thumbnail else '',
        }
    })
helper function: given an image, return the json to pass back to the
    image chooser panel