/**
     * Helper class to traverse graph. Required to make the containing method thread-safe
     * and yet use class level data to lessen stack usage in recursion
     */
    private class ClasspathGraphVisitor {
        MetadataGraph graph;

        ClasspathContainer cpc;

        List<MetadataGraphVertex> visited;

     *
     * This callback is intended to allow extensions to perform cleanup of any
     * allocated external resources after the build. It is invoked on best-effort
     * basis and may be missed due to an Error or RuntimeException in Maven core
     * code.
     *
     * @param session the Maven session
     * @throws MavenExecutionException in case of issue
     * @since 3.2.1, MNG-5389
     */