} else {
			versions = append(versions, fi)
			allVersionIDs = append(allVersionIDs, fi.VersionID)
		}
	}
	buf, err := xl.AppendTo(nil)
	if err != nil {
		t.Fatalf("Failed to serialize xlmeta %v", err)
	}
	fivs, err := getFileInfoVersions(buf, basefi.Volume, basefi.Name, false)
	if err != nil {
		t.Fatalf("getFileInfoVersions failed: %v", err)
	}
	chkNumVersions := func(fis []FileInfo) bool {

  @GwtIncompatible // SerializableTester
  public void testLexicographicalComparatorSerializable() {
    Comparator<byte[]> comparator = SignedBytes.lexicographicalComparator();
    assertThat(SerializableTester.reserialize(comparator)).isSameInstanceAs(comparator);
  }

  public void testSortDescending() {
    testSortDescending(new byte[] {}, new byte[] {});
    testSortDescending(new byte[] {1}, new byte[] {1});

import org.jspecify.annotations.Nullable;

/**
 * Provides static methods for serializing collection classes.
 *
 * <p>This class assists the implementation of collection classes. Do not use this class to
 * serialize collections that are defined elsewhere.
 *
 * @author Jared Levy
 */
@GwtIncompatible
@J2ktIncompatible
final class Serialization {
  private Serialization() {}

  /**

    // Write out all elements in the proper order.
    for (int i = 0; i < length; i++) {
      s.writeDouble(get(i));
    }
  }

  /** Reconstitutes the instance from a stream (that is, deserializes it). */
  private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
    s.defaultReadObject();

    int length = s.readInt();

   */
  private void writeObject(ObjectOutputStream s) throws IOException {
    s.defaultWriteObject();

    s.writeDouble(get());
  }

  /** Reconstitutes the instance from a stream (that is, deserializes it). */
  private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
    s.defaultReadObject();

    set(s.readDouble());
  }

     * @throws Exception
     */
    @Test
    public void testSerialize() throws Exception {
        list.addLast("1");
        list.addLast("2");
        list.addLast("3");
        assertThat(SerializeUtil.serialize(list), is(notNullValue()));
    }

    /**
     * @throws Exception
     */
    @Test
    public void testSet() throws Exception {
        list.addLast("1");
        list.addLast("2");

    ObjectInputStream in = new ObjectInputStream(new ByteArrayInputStream(serializedForm));

    ImmutableSet<?> deserialized = (ImmutableSet<?>) in.readObject();
    EnumSet<?> delegate = (EnumSet<?>) in.readObject();

    assertEquals(original, deserialized);
    assertTrue(delegate.remove(SomeEnum.A));
    assertTrue(deserialized.contains(SomeEnum.A));
  }

  @GwtIncompatible
  @J2ktIncompatible

```

</div>

Then go to the `/docs` UI, you will see that **FastAPI** is using these **models** to **document** the API, and it will use them to **serialize** and **validate** the data too.

<div class="screenshot">
<img src="/img/tutorial/sql-databases/image01.png">
</div>

## Update the App with Multiple Models { #update-the-app-with-multiple-models }

import static com.google.common.collect.Maps.immutableEntry;
import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;
import static com.google.common.testing.SerializableTester.reserialize;
import static com.google.common.truth.Truth.assertThat;
import static com.google.common.truth.Truth.assertWithMessage;
import static java.util.Arrays.asList;
import static java.util.Collections.singletonMap;

import org.jspecify.annotations.Nullable;

/**
 * Provides static methods for serializing collection classes.
 *
 * <p>This class assists the implementation of collection classes. Do not use this class to
 * serialize collections that are defined elsewhere.
 *
 * @author Jared Levy
 */
@GwtIncompatible
@J2ktIncompatible
final class Serialization {
  private Serialization() {}

  /**