code: public Optional<T> updateResource() {
          return JMOptional.getOptional(JMRestfulResource
                  .getStringWithRestOrClasspathOrFilePath(restfulResourceUrl))
                  .filter(getEquals(cachedJsonString).negate())
                  .filter(peek(this::setJsonStringCache))
                  .map(jsonString -> JMJson.withJsonString(jsonString,
                          typeReference))
                  .filter(peek(resource -> this.cachedResource = resource));
      }
docs: Update resource optional.
  
  @return the optional