static Map<String, String> markerLabels() {
        String testcontainersVersion = TESTCONTAINERS_VERSION == null ? "unspecified" : TESTCONTAINERS_VERSION;

        Map<String, String> labels = new HashMap<>();
        labels.put(TESTCONTAINERS_LABEL, "true");
        labels.put(TESTCONTAINERS_LANG_LABEL, "java");
        labels.put(TESTCONTAINERS_VERSION_LABEL, testcontainersVersion);
        return Collections.unmodifiableMap(labels);
    }
Singleton class that provides initialized Docker clients.
<p>
The correct client configuration to use will be determined on first use, and cached thereafter.
core/src/main/java/org/testcontainers/DockerClientFactory.java