public void checkPackageFiles(Set packageFiles, Set missingFiles)
public void checkPackageFiles(Set packageFiles, Set missingFiles, MetsManifest manifest)
    public void checkPackageFiles(Set packageFiles, Set missingFiles)        throws PackageValidationException, CrosswalkException    {        // This is where a subclass would arrange to use or ignore        // any "extra" files added to its type of package.    }