def METHOD_NAME(client, resource_group_name, webpubsub_name, hub_name, user_id):
    service_client = _get_service_client(client, resource_group_name, webpubsub_name)
    res = service_client.send_request(build_user_exists_request(hub_name, user_id))
    return _get_existence_response(res.status_code == 200)