How to use the awscrt.io.DefaultHostResolver function in awscrt

def _new_client_connection(self, secure, proxy_options=None):
        if secure:
            tls_ctx_opt = TlsContextOptions()
            tls_ctx_opt.override_default_trust_store_from_path(None, 'test/resources/unittests.crt')
            tls_ctx = ClientTlsContext(tls_ctx_opt)
            tls_conn_opt = tls_ctx.new_connection_options()
            tls_conn_opt.set_server_name(self.hostname)
        else:
            tls_conn_opt = None

        event_loop_group = EventLoopGroup()
        host_resolver = DefaultHostResolver(event_loop_group)
        bootstrap = ClientBootstrap(event_loop_group, host_resolver)
        connection_future = HttpClientConnection.new(host_name=self.hostname,
                                                     port=self.port,
                                                     bootstrap=bootstrap,
                                                     tls_connection_options=tls_conn_opt,
                                                     proxy_options=proxy_options)
        return connection_future.result(self.timeout)

def _test_connection(self):
        config = Config.get()
        elg = EventLoopGroup()
        resolver = DefaultHostResolver(elg)
        bootstrap = ClientBootstrap(elg, resolver)

        tls_opts = TlsContextOptions.create_client_with_mtls(config.cert, config.key)
        tls = ClientTlsContext(tls_opts)

        client = Client(bootstrap, tls)
        connection = Connection(
            client=client,
            client_id=create_client_id(),
            host_name=config.endpoint,
            port=8883)
        connection.connect().result(TIMEOUT)
        return connection

def test_mtls_from_path(self):
        config = Config.get()
        elg = EventLoopGroup()
        resolver = DefaultHostResolver(elg)
        bootstrap = ClientBootstrap(elg, resolver)

        # test "from path" builder by writing secrets to tempfiles
        tmp_dirpath = tempfile.mkdtemp()
        try:
            cert_filepath = os.path.join(tmp_dirpath, 'cert')
            with open(cert_filepath, 'wb') as cert_file:
                cert_file.write(config.cert)

            key_filepath = os.path.join(tmp_dirpath, 'key')
            with open(key_filepath, 'wb') as key_file:
                key_file.write(config.key)

            connection = awsiot_mqtt_connection_builder.mtls_from_path(
                cert_filepath=cert_filepath,
                pri_key_filepath=key_filepath,

def test_mtls_from_bytes(self):
        config = Config.get()
        elg = EventLoopGroup()
        resolver = DefaultHostResolver(elg)
        bootstrap = ClientBootstrap(elg, resolver)
        connection = awsiot_mqtt_connection_builder.mtls_from_bytes(
            cert_bytes=config.cert,
            pri_key_bytes=config.key,
            endpoint=config.endpoint,
            client_id=create_client_id(),
            client_bootstrap=bootstrap)
        self._test_connection(connection)

except Exception as e:
            print("Exception on input thread.")
            exit(e)
            break

if __name__ == '__main__':
    # Process input args
    args = parser.parse_args()
    thing_name = args.thing_name
    shadow_property = args.shadow_property
    io.init_logging(getattr(io.LogLevel, args.verbosity), 'stderr')

    # Spin up resources
    event_loop_group = io.EventLoopGroup(1)
    host_resolver = io.DefaultHostResolver(event_loop_group)
    client_bootstrap = io.ClientBootstrap(event_loop_group, host_resolver)

    if args.use_websocket == True:
        proxy_options = None
        if (args.proxy_host):
            proxy_options = http.HttpProxyOptions(host_name=args.proxy_host, port=args.proxy_port)

        credentials_provider = auth.AwsCredentialsProvider.new_default_chain(client_bootstrap)
        mqtt_connection = mqtt_connection_builder.websockets_with_default_aws_signing(
            endpoint=args.endpoint,
            client_bootstrap=client_bootstrap,
            region=args.signing_region,
            credentials_provider=credentials_provider,
            websocket_proxy_options=proxy_options,
            ca_filepath=args.root_ca,
            client_id=args.client_id,

time.sleep(1)

def waitForRegisterThingResponse():
    # Wait for the response.
    loopCount = 0
    while loopCount < 20 and registerThingResponse is None:
        if registerThingResponse is not None:
            break
        loopCount += 1
        print('Waiting... RegisterThingResponse: ' + json.dumps(registerThingResponse))
        time.sleep(1)

if __name__ == '__main__':
    # Spin up resources
    event_loop_group = io.EventLoopGroup(1)
    host_resolver = io.DefaultHostResolver(event_loop_group)
    client_bootstrap = io.ClientBootstrap(event_loop_group, host_resolver)

    if args.use_websocket == True:
        proxy_options = None
        if (args.proxy_host):
            proxy_options = http.HttpProxyOptions(host_name=args.proxy_host, port=args.proxy_port)

        credentials_provider = auth.AwsCredentialsProvider.new_default_chain(client_bootstrap)
        mqtt_connection = mqtt_connection_builder.websockets_with_default_aws_signing(
            endpoint=args.endpoint,
            client_bootstrap=client_bootstrap,
            region=args.signing_region,
            credentials_provider=credentials_provider,
            websocket_proxy_options=proxy_options,
            on_connection_interrupted=on_connection_interrupted,
            on_connection_resumed=on_connection_resumed,