[Python] How to convert Firestore timestamp to ISO 8601 in python?

I am writing a firebase cloud function in python to read data from firestore database and update it into the firebase realtime database, however I am facing an issue with converting the firestore datetime to ISO 8601 format so i can store the date in a JSON format. I believe there exists a library to do this in javascript but not in python. Any help would be greatly appreciated.

import datetime
from google.cloud import firestore

def serialize_datetime(dt):
""" Convert Firestore Timestamp or Python datetime to ISO 8601 string. """
if isinstance(dt, firestore.Timestamp):
return dt.to_pydatetime().isoformat()
elif isinstance(dt, datetime.datetime):
return dt.isoformat()
return dt

'order_datetime': serialize_datetime(order_data.get('orderDate')),
'expiry_datetime': serialize_datetime(order_data.get('deliveryDate')),

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