code: protected function loadMessages($category, $language)
      {
          if ($this->enableCaching) {
              $key = [
                  __CLASS__,
                  $category,
                  $language,
              ];
              $messages = $this->cache->get($key);
              if ($messages === false) {
                  $messages = $this->loadMessagesFromDb($category, $language);
                  $this->cache->set($key, $messages, $this->cachingDuration);
              }
  
              return $messages;
          }
  
          return $this->loadMessagesFromDb($category, $language);
      }
docs: Loads the message translation for the specified language and category.
  If translation for specific locale code such as `en-US` isn't found it
  tries more generic `en`.
  
  @param string $category the message category
  @param string $language the target language
  @return array the loaded messages. The keys are original messages, and the values
  are translated messages.