code: private final static String getManifestKeyForBundle(Bundle owningBundle) {
          URL manifestKeyURL = owningBundle.getEntry(MANIFESTPATH);
          if (manifestKeyURL == null) {
              //'bundle' did not have a manifest.
              throw new IllegalArgumentException(owningBundle.getSymbolicName());
          }
          String manifestKey = manifestKeyURL.toExternalForm();
          return manifestKey;
      }
docs: Simple little helper to get a unique string key for any bundle.
  <p>
  Currently uses the string form of the url for META-INF/MANIFEST.MF