client = mqtt.Client(client_id=client_id)

    # With Google Cloud IoT Core, the username field is ignored, and the
    # password field is used to transmit a JWT to authorize the device.
    client.username_pw_set(
        username="unused", password=create_jwt(project_id, private_key_file, algorithm)
    )

    # Enable SSL/TLS support.
    [b]client.tls_set(ca_certs=ca_certs, tls_version=ssl.PROTOCOL_TLSv1_2)[/b]