Let's continue from the previous example. We wanted to **annotate the function with one type**, but we wanted to be able to return from the function something that actually includes **more data**.

We want FastAPI to keep **filtering** the data using the response model. So that even though the function returns more data, the response will only include the fields declared in the response model.

import com.google.common.testing.SerializableTester;
import com.google.common.truth.IterableSubject;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.Keep;
import java.io.Serializable;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;

{* ../../docs_src/server_sent_events/tutorial005_py310.py hl[14] *}

## Détails techniques { #technical-details }

FastAPI met en œuvre certaines bonnes pratiques SSE prêtes à l’emploi.

    canceled = true
    stream?.closeLater(ErrorCode.CANCEL)
  }

  companion object {
    private const val CONNECTION = "connection"
    private const val HOST = "host"
    private const val KEEP_ALIVE = "keep-alive"
    private const val PROXY_CONNECTION = "proxy-connection"
    private const val TRANSFER_ENCODING = "transfer-encoding"
    private const val TE = "te"
    private const val ENCODING = "encoding"

      }
    }

    /**
     * Associates {@code key} with {@code value} in the built map. If the same key is put more than
     * once, {@link #buildOrThrow} will fail, while {@link #buildKeepingLast} will keep the last
     * value put for that key.
     */
    @CanIgnoreReturnValue
    public Builder<K, V> put(K key, V value) {
      ensureCapacity(size + 1);
      Entry<K, V> entry = entryOf(key, value);

   * state hurts system maintainability and testability. In cases when you have no choice while
   * interoperating with a legacy framework, this method helps to keep the code less ugly.
   *
   * @throws ExceptionInInitializerError if an exception is thrown during initialization of a class
   */
  public static void initialize(Class<?>... classes) {
    for (Class<?> clazz : classes) {

    }
  }

  @Override
  public int size() {
    return size;
  }

  // We're careful to put only E instances into the array in the mainline.
  // (In the backport, we don't need this suppression, but we keep it to minimize diffs.)
  @SuppressWarnings("unchecked")
  @Override
  public UnmodifiableIterator<E> iterator() {
    return asList().iterator();
  }

  @Override
  @Nullable Object[] internalArray() {

  }

  @ListFeature.Require(absent = SUPPORTS_ADD_WITH_INDEX)
  @CollectionSize.Require(absent = ZERO)
  /*
   * absent = ZERO isn't required, since unmodList.add() must
   * throw regardless, but it keeps the method name accurate.
   */
  public void testAddAtIndex_unsupportedPresent() {
    assertThrows(UnsupportedOperationException.class, () -> getList().add(0, e0()));
    expectUnchanged();
  }

Upgrading to OkHttp 4
=====================

OkHttp 4.x upgrades our implementation language from Java to Kotlin and keeps everything else the
same. We’ve chosen Kotlin because it gives us powerful new capabilities while integrating closely
with Java.

We spent a lot of time and energy on retaining strict compatibility with OkHttp 3.x. We’re even
keeping the package name the same: `okhttp3`!

There are three kinds of compatibility we’re tracking:

 * continues. See {@link QueueWorker#workOnQueue} for details.
 *
 * <p>{@code RuntimeException}s thrown by tasks are simply logged and the executor keeps trucking.
 * If an {@code Error} is thrown, the error will propagate and execution will stop until it is
 * restarted by a call to {@link #execute}.
 */
@J2ktIncompatible
@GwtIncompatible