Creating a Google Adsense AdUnit with the Python API?

Question

How do you use the Python Adsense Management API to create adunits?

Based on documentation and some examples I've found, it should be something like:

#!/usr/bin/env python
"""
pip install google-auth google-auth-oauthlib google-auth-httplib2
"""

from google.oauth2 import service_account
from googleapiclient.discovery import build

account_id = 'pub-<id>'

ad_client_id = 'ca-pub-<id>'

# Load credentials from the downloaded JSON file
credentials = service_account.Credentials.from_service_account_file('myservicekey.json', scopes=['https://www.googleapis.com/auth/adsense'])

# Create AdSense API service
adsense_service = build('adsense', 'v2', credentials=credentials)

# Define the ad client data
ad_client_data = {
    "productCode": "AFC",
    "supportsReporting": True,
    "kind": "adsense#adClient",
}

# Define the ad unit data
ad_unit_data = {
    "contentAdsSettings": {
        "backupOption": {
            "type": "USE_DEFAULT"
        },
        "size": "SIZE_UNSPECIFIED"
    },
    "name": "Test Ad 123",
    "customStyle": {
        "colors": {
            "border": "#ffffff",
            "title": "#333333",
            "background": "#ffffff",
            "text": "#666666",
            "url": "#1a0dab"
        }
    },
    "mobileContentAdsSettings": {
        "size": "SIZE_UNSPECIFIED"
    },
    "settings": {
        "size": ["SIZE_UNSPECIFIED"]
    }
}

# Create the ad unit, none of these work.
# ad_unit = adsense_service.accounts().adunits().create(body=ad_unit_data, parent=ad_client['name']).execute()
# ad_unit = adsense_service.accounts().adunits().create(body=ad_unit_data, parent=f'accounts/{account_id}/adclients/{ad_client_id}').execute()
# ad_unit = adsense_service.accounts().adclients().adunits().create(body=ad_unit_data, parent=f'accounts/{account_id}/adclients/{ad_client_id}').execute()
# ad_unit = adsense_service.accounts().adunits().insert(body=ad_unit_data, accountId=account_id, adClientId=ad_client_id).execute()
ad_unit = adsense_service.accounts().adclients().adunits().create(body=ad_unit_data, parent=f'accounts/{account_id}/adclients/{ad_client_id}').execute()

However, all variations of the final call to create ad_unit fail with the error AttributeError: 'Resource' object has no attribute 'create' or AttributeError: 'Resource' object has no attribute 'insert' if I try to use the older insert() method.

My call appears to correctly follow the accounts.adclients.adunits.create path listed in the v2 docs.

What am I doing wrong? Why is the create() method missing?