code: public List<File> getInactiveHistory() throws PatchingException {
          if (validHistory == null) {
              walk();
          }
          final File[] inactiveDirs = installedIdentity.getInstalledImage().getPatchesDir().listFiles(new FileFilter() {
              @Override
              public boolean accept(File pathname) {
                  return pathname.isDirectory() && !validHistory.contains(pathname.getName());
              }
          });
          return inactiveDirs == null ? Collections.<File>emptyList() : Arrays.asList(inactiveDirs);
      }
docs: Get the inactive history directories.
  
  @return the inactive history