code: public static void unregister(String ID) {
          displayNameCache.remove(new CaseInsensitiveString(ID));
          registry.remove(ID);
      }
docs: Unregisters a transliterator or class.  This may be either
  a system transliterator or a user transliterator or class.
  
  @param ID the ID of the transliterator or class
  @see #registerClass