def METHOD_NAME(use_mtls):
    # The interceptor adds 'showcase-trailer' client metadata. Showcase server
    # echos any metadata with key 'showcase-trailer', so the same metadata
    # should appear as trailing metadata in the response.
    interceptor = MetadataClientInterceptor("showcase-trailer", "intercepted")
    host = "localhost:7469"
    channel = (
        grpc.secure_channel(host, ssl_credentials)
        if use_mtls
        else grpc.insecure_channel(host)
    )
    intercept_channel = grpc.intercept_channel(channel, interceptor)
    transport = EchoClient.get_transport_class("grpc")(
        channel=intercept_channel
    )
    return EchoClient(transport=transport)