def autolinks_simple(url):
    u_url=url.lower()
    if '@' in url and not '://' in url:
        return '<a href="mailto:%s">%s</a>' % (url, url)
    elif u_url.endswith(('.jpg','.jpeg','.gif','.png')):
        return '<img src="%s" controls />' % url
    elif u_url.endswith(('.mp4','.mpeg','.mov','.ogv')):
        return '<video src="%s" controls></video>' % url
    elif u_url.endswith(('.mp3','.wav','.ogg')):
        return '<audio src="%s" controls></audio>' % url
    return '<a href="%s">%s</a>' % (url,url)
it automatically converts the url to link,
dataset/ETHPy150Open uwdata/termite-data-server/web2py/gluon/contrib/markmin/markmin2html.py/autolinks_simple