def subscribe(self, post_url, callback=None, pickle=True, timeout=None):
post_id, post_site, post_type = fetch_post_id_and_site_from_url(post_url)
if post_site not in GlobalVars.site_id_dict:
log("warning", "unknown site {} when subscribing to {}".format(post_site, post_url))
return
if post_type == "answer":
question_id = datahandling.get_post_site_id_link((post_id, post_site, post_type))
if question_id is None:
return