[Guava's philosophy](https://github.com/google/guava/wiki/PhilosophyExplained), and
            I strongly believe that this proposal aligns with it.
          required: true
        - label: >
            I have visited the [idea graveyard](https://github.com/google/guava/wiki/IdeaGraveyard),
            and did not see anything similar to this idea.

 * class CrawlingService extends AbstractScheduledService {
 *   private Set<Uri> visited;
 *   private Queue<Uri> toCrawl;
 *   protected void startUp() throws Exception {
 *     toCrawl = readStartingUris();
 *   }
 *
 *   protected void runOneIteration() throws Exception {
 *     Uri uri = toCrawl.remove();
 *     Collection<Uri> newUris = crawl(uri);
 *     visited.add(uri);
 *     for (Uri newUri : newUris) {

      return true;
    }
    return hasCycle(network.asGraph());
  }

  /**
   * Performs a traversal of the nodes reachable from {@code startNode}. If we ever reach a node
   * we've already visited (following only outgoing edges and without reusing edges), we know
   * there's a cycle in the graph.
   */
  private static <N> boolean subgraphHasCycle(

      return true;
    }
    return hasCycle(network.asGraph());
  }

  /**
   * Performs a traversal of the nodes reachable from {@code startNode}. If we ever reach a node
   * we've already visited (following only outgoing edges and without reusing edges), we know
   * there's a cycle in the graph.
   */
  private static <N> boolean subgraphHasCycle(

        private int indexToRemove = ABSENT;
        private int expectedModCount = biMap.modCount;

        // Calls to setValue on inverse entries can move already-visited entries to the end.
        // Make sure we don't visit those.
        private int remaining = biMap.size;

        private void checkForComodification() {
          if (biMap.modCount != expectedModCount) {

            return null;
        }

        @Override
        public void saveSession(String sessionId) {
            // Do nothing in test
        }

        @Override
        public boolean visited(OpenSearchUrlQueue urlQueue) {
            return false;
        }

        @Override
        public void generateUrlQueues(String sessionId, String url) {
            // Do nothing in test
        }

        // check url
        if (crawlerContext.getRobotsTxtUrlSet().contains(robotTxtUrl)) {
            if (logger.isDebugEnabled()) {
                logger.debug("{} is already visited.", robotTxtUrl);
            }
            return;
        }

        if (logger.isInfoEnabled()) {
            logger.info("Checking URL: {}", robotTxtUrl);
        }
        // add url to a set

/**
 * Defines a hierarchical visitor for collecting dependency node trees.
 *
 * @since 4.0.0
 */
@Experimental
@Consumer
public interface NodeVisitor {
    /**
     * Starts the visit to the specified dependency node.
     *
     * @param node the dependency node to visit
     * @return <code>true</code> to visit the specified dependency node's children, <code>false</code> to skip the

    /**
     * Traverses this node and potentially its children using the specified visitor.
     *
     * @param visitor the visitor to call back, must not be {@code null}
     * @return {@code true} to visit siblings nodes of this node as well, {@code false} to skip siblings
     */
    boolean accept(@Nonnull NodeVisitor visitor);

    /**
     * Returns a new tree starting at this node, filtering the children.

        return queryBuilder.rewrite(queryShardContext);
    }

    @Override
    public void visit(final QueryBuilderVisitor visitor) {
        queryBuilder.visit(visitor);
    }

    @Override
    public XContentBuilder toXContent(final XContentBuilder builder, final Params params) throws IOException {