xPath = createXPath(f -> {});
    }

    public XPath createXPath(final Consumer<XPathFactory> builder) {
        try {
            final XPathFactory factory = XPathFactory.newInstance();
            builder.accept(factory);
            return factory.newXPath();
        } catch (final Exception e) {
            throw new CrawlerSystemException("Failed to create XPath instance.", e);
        }
    }

    /**

 * iterator} method only once, and should be tested using this class. Exceptions to this rule should
 * be clearly documented.
 *
 * <p>Note that although your APIs should be liberal in what they accept, your methods which
 * <i>return</i> iterables should make every attempt to return ones of the robust variety.
 *
 * <p>This testing utility is not thread-safe.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible

    CacheTesting.checkRecency(
        cache,
        MAX_SIZE,
        new Receiver<ReferenceEntry<Integer, Integer>>() {
          @Override
          public void accept(ReferenceEntry<Integer, Integer> entry) {
            cache.getUnchecked(entry.getKey());
          }
        });
  }

  public void testUpdateRecency_onInvalidate() {

        return sb.toString();
    }

    // ===================================================================================
    //                                                                            Accessor
    //                                                                            ========
    public String getContent() {
        checkSpecifiedProperty("content");
        return convertEmptyToNull(content);
    }

     *
     * @return The effective identifier of the model, never {@code null}.
     */
    public String getId() {
        // if source is null, it is the super model, which can be accessed via empty string
        return Objects.toString(source, "");
    }

    @Override
    public String toString() {
        return String.valueOf(model);
    }

 */
@GwtIncompatible // not worth using in GWT for now
@ElementTypesAreNonnullByDefault
class CompactHashSet<E extends @Nullable Object> extends AbstractSet<E> implements Serializable {
  // TODO(user): cache all field accesses in local vars

  /** Creates an empty {@code CompactHashSet} instance. */
  public static <E extends @Nullable Object> CompactHashSet<E> create() {
    return new CompactHashSet<>();
  }

  /**

            .put("CDN_LOOP", "CDN-Loop")
            .put("ETAG", "ETag")
            .put("SOURCE_MAP", "SourceMap")
            .put("SEC_CH_UA_WOW64", "Sec-CH-UA-WoW64")
            .put("SEC_WEBSOCKET_ACCEPT", "Sec-WebSocket-Accept")
            .put("SEC_WEBSOCKET_EXTENSIONS", "Sec-WebSocket-Extensions")
            .put("SEC_WEBSOCKET_KEY", "Sec-WebSocket-Key")
            .put("SEC_WEBSOCKET_PROTOCOL", "Sec-WebSocket-Protocol")

            .put("CDN_LOOP", "CDN-Loop")
            .put("ETAG", "ETag")
            .put("SOURCE_MAP", "SourceMap")
            .put("SEC_CH_UA_WOW64", "Sec-CH-UA-WoW64")
            .put("SEC_WEBSOCKET_ACCEPT", "Sec-WebSocket-Accept")
            .put("SEC_WEBSOCKET_EXTENSIONS", "Sec-WebSocket-Extensions")
            .put("SEC_WEBSOCKET_KEY", "Sec-WebSocket-Key")
            .put("SEC_WEBSOCKET_PROTOCOL", "Sec-WebSocket-Protocol")

                    log.error("Failed to create child URL", e);
                    continue;
                }
            }

            try ( SmbResource r = adapt(fe) ) {
                if ( this.filter.accept(r) ) {
                    return r;
                }
            }
            catch ( MalformedURLException e ) {
                log.error("Failed to create child URL", e);
                continue;
            }

        return sb.toString();
    }

    // ===================================================================================
    //                                                                            Accessor
    //                                                                            ========
    public Long getCreatedTime() {
        checkSpecifiedProperty("createdTime");
        return createdTime;
    }