Mark everything shared with guest account as unwatched.

mark_guest_unwatched.py

from plexapi.server import PlexServer
import requests

# Edit these
PLEX_URL = ''
PLEX_TOKEN = ''
# 

sess = requests.Session()
sess.verify = False
plex = PlexServer(PLEX_URL, PLEX_TOKEN, session=sess)

guest = plex.myPlexAccount().user("Guest")
token = guest.get_token(plex.machineIdentifier)
guest_plex = PlexServer(PLEX_URL, token, session=sess)
guest_sections = guest_plex.library.sections()

for section in guest_sections:
    print("Marking section: {} unwatched.".format(section.title))
    for items in section.all():
        print("Marking item: {} unwatched.".format(items.title))
        items.markUnwatched()