def sign_url(unsigned_url):
    if ks:
        unsigned_url += ('/ks/%s' % ks)
    if referrer:
        unsigned_url += ('?referrer=%s' % referrer)
    return unsigned_url
def sign_url(unsigned_url):
    if ks:
        unsigned_url += ('/ks/%s' % ks)
    if referrer:
        unsigned_url += ('?referrer=%s' % referrer)
    return unsigned_url