docs: private HashSet<String> get(String id) throws IOException {
      if (collectionCachePath != null) {
        Date date = clear();
        if (idToVersion.containsKey(id)) {
          String version = idToVersion.get(id);
          expirationVersion.put(version, date.getTime() + (1000 * lifeTime));
          MtasSolrCollectionCacheItem newItem = read(version, date.getTime());
          if (newItem != null && newItem.id.equals(id)) {
            return newItem.data;
          } else {
            log.error("couldn't get " + version);
            // delete file and remove from index
            if (!collectionCachePath.resolve(version).toFile().delete()) {
              log.debug("couldn't delete " + version);
            }
            idToVersion.remove(id);
            expirationVersion.remove(version);
            versionToItem.remove(version);
          }
        } else {
          log.error("doesn't exist anymore");
        }
        return null;
      } else
  
      {
        throw new IOException("no cachePath available, can't get data");
      }
    }