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);

):
    return [item, sub_item]


@app.post("/with-duplicates")
async def with_duplicates(item: Item, item2: Item = Depends(duplicate_dependency)):
    return [item, item2]


@app.post("/no-duplicates")
async def no_duplicates(item: Item, item2: Item = Depends(dependency)):
    return [item, item2]


@app.post("/with-duplicates-sub")
async def no_duplicates_sub(

    @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 =

        }
    }

    @Override
    public List<String> convert(final String text, final String field, final String... lang) throws IOException {
        // Use LinkedHashSet to maintain insertion order while eliminating duplicates
        final Set<String> resultSet = new LinkedHashSet<>();
        resultSet.add(text);

        // Start with the original text as the first input
        List<String> currentInputs = new ArrayList<>();

        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");

     * <p>This method performs the following validations:
     * <ul>
     *   <li>Allows null input (returns null)</li>
     *   <li>Ensures no duplicate repositories exist in the list</li>
     *   <li>Ensures no null repository entries exist in the list</li>
     * </ul>
     *
     * <p>Duplicate detection is based on the {@code RemoteRepository#equals(Object)}
     * method, which typically compares repository IDs and URLs.
     *

Then we can declare `tags` as a set of strings:

{* ../../docs_src/body_nested_models/tutorial003_py310.py hl[12] *}

With this, even if you receive a request with duplicate data, it will be converted to a set of unique items.

And whenever you output that data, even if the source had duplicates, it will be output as a set of unique items.

And it will be annotated / documented accordingly too.

## Nested Models { #nested-models }

 * 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.
 *

    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();

        assertTrue(data.getChildUrlSet().contains(child2));
    }

    public void test_childUrlSetNoDuplicates() {
        // Test that child URL set does not allow duplicates
        ResponseData data = new ResponseData();

        RequestData child = new RequestData();
        child.setMethod(Method.GET);
        child.setUrl("https://example.com/page1");