public RestClusterClient<StandaloneClusterId> getRestClusterClient() {
        if (restClusterClient != null) {
            return restClusterClient;
        }
        checkState(
                jobManager.isRunning(),
                "Cluster client should only be retrieved for a running cluster");
        try {
            final Configuration clientConfiguration = new Configuration();
            clientConfiguration.set(RestOptions.ADDRESS, jobManager.getHost());
            clientConfiguration.set(
                    RestOptions.PORT, jobManager.getMappedPort(JOB_MANAGER_REST_PORT));
            this.restClusterClient =
                    new RestClusterClient<>(clientConfiguration, StandaloneClusterId.getInstance());
        } catch (Exception e) {
            throw new IllegalStateException(
                    "Failed to create client for Flink container cluster", e);
        }
        return restClusterClient;
    }
Get {@link RestClusterClient} connected to this FlinkContainer.

<p>This method lazily initializes the REST client on-demand.
inlong-sort/sort-end-to-end-tests/sort-end-to-end-tests-v1.13/src/test/java/org/apache/inlong/sort/tests/utils/FlinkContainerTestEnv.java