code: public static boolean removeExtension(String extensionName) {
          if (extensionName == null) {
              throw new IllegalArgumentException(
                              "Parameter 'extensionName' can not be null");
          }
          HashMap<String, String> ext = extensions.get();
          return ext == null ? false : ext.remove(extensionName) != null;
      }
docs: Removes an extension key/value from the context
  
  @param extensionName
  String extensionName associated with the registered extension.
  @throws IllegalArgumentException
  if parameter <code>extensionName</code> is <code>null</code>.