code: public void registerCharsetMapping(String contentType, String charSet) {
      if (knownCharsets.contains(contentType)) {
        log.warn("{} is already registered; re-registering");
      }
  
      knownCharsets.put(contentType, charSet);
    }
docs: Register a new contentType to charSet mapping.
  @param contentType Content-type to register
  @param charSet charSet associated with the content-type