Python SDK bulk user creation hitting 429 despite backoff

Parsing a CSV to create users with the Genesys Cloud Python SDK. The loop works for the first 50 records, then it starts returning 429 errors. I’ve added a time.sleep(1) between calls, but it’s not helping. Here’s the snippet:

for row in csv_data:
 user = models.UserCreateRequest(...)
 api_instance.create_user(user)
 time.sleep(1)

Is there a specific rate limit for user creation I’m missing, or is the SDK client not handling the retry logic correctly?