Python SDK `bulk_create_users` hangs on 503

Running a script to import 2k agents from a CSV using genesyscloud_users_api.bulk_create_users. It works fine for batches of 50 but throws a 503 Service Unavailable around the 200th record. The SDK isn’t catching the retry logic properly. Here’s the loop:

for chunk in chunks(users, 50):
 api_response = users_api.bulk_create_users(body=chunk)

Is there a specific backoff setting I need to pass or am I hitting a hard rate limit that the SDK doesn’t handle?