Change types for python3.10 compatability

ai_ta_backend/service/nomic_service.py

@@ -1,6 +1,7 @@
 import datetime
 import os
 import time
+from typing import Union
 
 import backoff
 import nomic
@@ -71,7 +72,7 @@ def __init__(self, sentry: SentryService, sql: SQLDatabase):
                         raise_on_giveup=False,
                         giveup=giveup_hdlr,
                         on_backoff=backoff_hdlr)
-  def log_convo_to_nomic(self, course_name: str, conversation) -> str | None:
+  def log_convo_to_nomic(self, course_name: str, conversation) -> Union[str, None]:
     # nomic.login(os.getenv('NOMIC_API_KEY'))  # login during start of flask app
     NOMIC_MAP_NAME_PREFIX = 'Conversation Map for '
     """