public @Nullable URLClassLoader getLibraryClassLoader() {
    return libraryClassLoader;
  }
Gets the {@link ClassLoader} that can be used to load classes found in JARs
in the stack's library folder.

@return the class loader for 3rd party JARs supplied by the stack or
        {@code null} if there are no libraries for this stack.
ambari-server/src/main/java/org/apache/ambari/server/state/StackInfo.java