private static boolean isManifestToSeal(final String packageName, final Manifest manifest) {
        final Optional<Attributes> perEntryAttributes =
                Optional.ofNullable(manifest.getAttributes(packageName.replace('.', '/').concat("/")));
        final Attributes mainAttributes = manifest.getMainAttributes();

        return "true".equalsIgnoreCase(
                getEffectiveAttribute(mainAttributes, perEntryAttributes, Attributes.Name.SEALED));
    }
Finds resources recognized as the given name.

<p>Note that {@link java.net.URLClassLoader#findResources} is public while {@link java.lang.ClassLoader#findResources}
is protected.
embulk-core/src/main/java/org/embulk/cli/SelfContainedJarAwareURLClassLoader.java