code: static Map<String, String> getVersionAttributes(URL url) throws IOException {
          Map<String, String> ret = new LinkedHashMap<>();
          try (InputStream inputStream = url.openStream()) {
              Manifest manifest = new Manifest(inputStream);
              Attributes attributes = manifest.getMainAttributes();
              for (String key : VERSION_ATTRIBUTES) {
                  final String value = attributes.getValue(key);
                  ret.put(key, value == null ? UNKNOWN_VALUE : value);
              }
          }
          return ret;
      }
docs: For the sake of unit testing
  
  @param url the URL to load the MANIFEST.MF file from
  @return a {@link Map} of attributes
  @throws IOException on problems with reading {@code /META-INF/MANIFEST.MF} file from the given {@code url}