AWS IoT Device SDK for Python without CA certificate

Is it possible to connect to MQTT over websockets via the AWS IoT Device SDK for Python without a CA certificate, using AWS Access Key ID and AWS Secret Access Key instead? I have it working that way within a javascript app and a java app, I'm wondering if it's possible from Python as well?

from AWSIoTPythonSDK.MQTTLib import AWSIoTMQTTClient

clientId = "my-client-id"
clientEndpoint = "my-client-endpoint"
accessKeyId = "my-access-key-id"
secretAccessKey = "my-secret-access-key"

myAWSIoTMQTTClient = AWSIoTMQTTClient(clientId, useWebsocket=True)
myAWSIoTMQTTClient.configureEndpoint(clientEndpoint, 443)
myAWSIoTMQTTClient.configureIAMCredentials(accessKeyId, secretAccessKey)

The connection times out. It may be because my router does not allow IPv6 (read here). I tried this work around, but it still is not working, since it seems to need a CA cert.

Is what I'm trying to do actually possible?