docs: private String getCachedETag(HttpHost host, String file) {
          Map<String, Object> cachedETags = readCachedETags();
  
          @SuppressWarnings("unchecked")
          Map<String, Object> hostMap =
                  (Map<String, Object>)cachedETags.get(host.toURI());
          if (hostMap == null) {
              return null;
          }
  
          @SuppressWarnings("unchecked")
          Map<String, String> etagMap = (Map<String, String>)hostMap.get(file);
          if (etagMap == null) {
              return null;
          }
  
          return etagMap.get("ETag");
      }