# Return a Response Directly { #return-a-response-directly }

When you create a **FastAPI** *path operation* you can normally return any data from it: a `dict`, a `list`, a Pydantic model, a database model, etc.

If you declare a [Response Model](../tutorial/response-model.md) FastAPI will use it to serialize the data to JSON, using Pydantic.

    DescendingTestMapGenerator(TestSortedMapGenerator<K, V> delegate) {
      super(delegate);
    }

    @Override
    public NavigableMap<K, V> create(Object... entries) {
      NavigableMap<K, V> map = (NavigableMap<K, V>) delegate.create(entries);
      return map.descendingMap();
    }

    @Override
    public Iterable<Entry<K, V>> order(List<Entry<K, V>> insertionOrder) {

class DfsReferralRequestBufferTest {

    private DfsReferralRequestBuffer buffer;

    @Nested
    @DisplayName("Constructor Tests")
    class ConstructorTests {

        @Test
        @DisplayName("Should create buffer with simple path and referral level")
        void testConstructorWithSimplePath() {
            String path = "\\\\server\\share";
            int maxReferralLevel = 3;

    }

    @Test
    void crudTest() {
        testCreate();
        testRead();
        testUpdate();
        testDelete();
    }

    @Test
    void testDownloadCsv_ok() {
        // First create some test data
        for (int i = 0; i < 3; i++) {
            final Map<String, Object> requestBody = createTestParam(i + 100);
            checkPostMethod(requestBody, getItemEndpointSuffix());
        }

    expectUnchanged();
  }

  @CollectionFeature.Require(SUPPORTS_ADD)
  public void testAddAll_emptyMultiset() {
    assertFalse(getMultiset().addAll(getSubjectGenerator().create()));
    expectUnchanged();
  }

  @CollectionFeature.Require(SUPPORTS_ADD)
  public void testAddAll_nonEmptyList() {
    assertTrue(getMultiset().addAll(asList(e3(), e4(), e3())));

  /**
   * Returns the value associated with {@code key} in this cache, obtaining that value from {@code
   * loader} if necessary. The method improves upon the conventional "if cached, return; otherwise
   * create, cache and return" pattern. For further improvements, use {@link LoadingCache} and its
   * {@link LoadingCache#get(Object) get(K)} method instead of this one.
   *

    * `description`: a `str` with a short description for the external docs.
    * `url` (**required**): a `str` with the URL for the external documentation.

### Create metadata for tags { #create-metadata-for-tags }

Let's try that in an example with tags for `users` and `items`.

Create metadata for your tags and pass it to the `openapi_tags` parameter:

{* ../../docs_src/metadata/tutorial004_py310.py hl[3:16,18] *}

  }

  /**
   * Returns a builder that creates immutable sorted sets whose elements are ordered by the reverse
   * of their natural ordering.
   */
  public static <E extends Comparable<?>> Builder<E> reverseOrder() {
    return new Builder<>(Collections.reverseOrder());
  }

  /**
   * Returns a builder that creates immutable sorted sets whose elements are ordered by their

  }

  public static <E> TestSetGenerator<E> newInstance(TestSetGenerator<E> delegate) {
    return new ReserializingTestSetGenerator<>(delegate);
  }

  @Override
  public Set<E> create(Object... elements) {
    return (Set<E>) super.create(elements);
  }

    TreeRangeMap<Integer, Integer> empty = TreeRangeMap.create();
    TreeRangeMap<Integer, Integer> nonEmpty = TreeRangeMap.create();
    nonEmpty.put(Range.all(), 1);
    TreeRangeMap<Integer, Integer> coalesced = TreeRangeMap.create();
    coalesced.put(Range.atLeast(1), 1);
    coalesced.putCoalescing(Range.atMost(1), 1);
    TreeRangeMap<Integer, Integer> differentValues = TreeRangeMap.create();
    differentValues.put(Range.closedOpen(1, 2), 2);