Cloud Function Accessing ObjectId of Pubsub Notification

test_cf.py

def run(event, context):
    """
    Sample code of a cloud function entrypoint that is called when a message
    is published to a topic. This is run when there is a notification on a prefix 
    in cloud storage.
    
    The message (event) contains the path to the objectId invoking the message.
    """
    
    event_filename = event["attributes"]["objectId"]
    event_bucket = event["attributes"]["bucketId"]
    
    print("file `{}` was triggered in bucket `{}`".format(event_filename, event_bucket))

    print("This Function was triggered by messageId {} published at {}".format(
        context.event_id, context.timestamp))
    
    return