[Python] Can't decode event data in Cloud Run Function with a Firestore trigger

I have deployed a 2nd Gen Cloud Run Function with a Firestore trigger, on the google.cloud.datastore.entity.v1.written event. I have used the sample code shown in Google Cloud documentation:

from cloudevents.http import CloudEvent
import functions_framework
from google.events.cloud import firestore


@functions_framework.cloud_event
def hello_firestore(cloud_event: CloudEvent) -> None:
"""Triggers by a change to a Firestore document.

Args:
cloud_event: cloud event with information on the firestore event trigger
"""
firestore_payload = firestore.DocumentEventData()
firestore_payload._pb.ParseFromString(cloud_event.data)

print(f"Function triggered by change to: {cloud_event['source']}")

print("\nOld value:")
print(firestore_payload.old_value)

print("\nNew value:")
print(firestore_payload.value)



And here's the list of the dependencies residing in the requirements.txt file:

functions-framework==3.3.0
google-events==0.13.0
google-api-core==2.6.0
protobuf==5.28.3
cloudevents==1.9.0


However, every time a Firestore event comes in, the Cloud Run Function fails with the following error:

Traceback (most recent call last):
File "/layers/google.python.pip/pip/lib/python3.10/site-packages/flask/app.py", line 2190, in wsgi_app
response = self.full_dispatch_request()
File "/layers/google.python.pip/pip/lib/python3.10/site-packages/flask/app.py", line 1486, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/layers/google.python.pip/pip/lib/python3.10/site-packages/flask/app.py", line 1484, in full_dispatch_request
rv = self.dispatch_request()
File "/layers/google.python.pip/pip/lib/python3.10/site-packages/flask/app.py", line 1469, in dispatch_request
return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
File "/layers/google.python.pip/pip/lib/python3.10/site-packages/functions_framework/__init__.py", line 174, in view_func
function(event)
File "/layers/google.python.pip/pip/lib/python3.10/site-packages/functions_framework/__init__.py", line 70, in wrapper
return func(*args, **kwargs)
File "/workspace/main.py", line 13, in hello_firestore
firestore_payload._pb.ParseFromString(cloud_event.data)
google.protobuf.message.DecodeError: Error parsing message with type 'google.events.cloud.firestore.v1.DocumentEventData'


Documentation also suggests including the proto dependencies in the source, which is something I've done but this doesn't seem to solve the issue, either. I'm sharing a screenshot of the structure, in case I have placed the proto dependencies, incorrectly:



I'm running out of ideas so would appreciate any help in case anyone has experienced similar issues and managed to resolve them.

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