return false; // This is the first occurrence
                    }
                })
                .toList();

        // Remove duplicates while preserving formatting
        duplicates.forEach(DomUtils::removeElement);

        return !duplicates.isEmpty();
    }

    private String createDependencyKey(Element dependency) {
        String groupId = dependency.childText(MavenPomElements.Elements.GROUP_ID);

    @SuppressWarnings("unchecked")
    E[] array = (E[]) elements.toArray();
    /*
     * For a Set, we guess that it contains no duplicates. That's just a guess for purpose of
     * sizing; if the Set uses different equality semantics, it might contain duplicates according
     * to equals(), and we will deduplicate those properly, albeit at some cost in allocations.
     */
    int expectedSize =

        assertEquals(cProject, sortedProjects.get(1));

        assertTrue(graph.getDownstreamProjects(aProject, false).contains(cProject));
    }

    // Test verifying that getDownstreamProjects does not contain duplicates.
    // This is a regression test for https://github.com/apache/maven/issues/2487.
    //
    // The graph is:
    // aProject -> bProject
    //        | -> dProject
    //        | -> eProject

        assertEquals("https://example.com/sitemap2.xml", sitemaps[1]);
    }

    public void test_addSitemapNoDuplicates() {
        // Test that addSitemap doesn't add duplicates
        RobotsTxt robotsTxt = new RobotsTxt();

        robotsTxt.addSitemap("https://example.com/sitemap.xml");
        robotsTxt.addSitemap("https://example.com/sitemap.xml");

		var res *Checksum
		for _, header := range trailing {
			var duplicates bool
			for _, t := range BaseChecksumTypes {
				if strings.EqualFold(t.Key(), header) {
					duplicates = res != nil
					res = NewChecksumWithType(t|ChecksumTrailing, "")
				}
			}
			if duplicates {
				return nil, ErrInvalidChecksum
			}
		}
		if res != nil {

     * q-quantile.
     *
     * @param indexes the quantile indexes, each of which must be in the inclusive range [0, q] for
     *     q-quantiles; the order of the indexes is unimportant, duplicates will be ignored, and the
     *     set will be snapshotted when this method is called
     * @throws IllegalArgumentException if {@code indexes} is empty
     */
    public ScaleAndIndexes indexes(int... indexes) {

    }
  }

  // TODO: test adding element of wrong type

  /**
   * Returns {@link Method} instances for the {@code setCount()} tests that assume multisets support
   * duplicates so that the test of {@code Multisets.forSet()} can suppress them.
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection
  public static List<Method> getSetCountDuplicateInitializingMethods() {
    return asList(

    public void test_duplicateUrlsInSitemap() {
        // Test handling of duplicate URLs in sitemap
        ResponseData responseData = new ResponseData();
        byte[] content = "<sitemap></sitemap>".getBytes();
        responseData.setResponseBody(content);

        SitemapUrl sitemap1 = new SitemapUrl();
        sitemap1.setLoc("https://example.com/duplicate");

        SitemapUrl sitemap2 = new SitemapUrl();

 * elements.
 *
 * <p>The collections created by {@link #createCollection()} may or may not allow duplicates. If the
 * collection, such as a {@link Set}, does not support duplicates, an added key-value pair will
 * replace an existing pair with the same key and value, if such a pair is present. With collections
 * like {@link List} that allow duplicates, the collection will keep the existing key-value pairs
 * while adding a new pair.
 *

			success: false,
		},
		// no duplicates, shall be parsed properly.
		{