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

If you don't declare a response model, FastAPI will use the `jsonable_encoder` explained in [JSON Compatible Encoder](../tutorial/encoder.md) and put it in a `JSONResponse`.

 * which contained the following notice:
 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

package com.google.common.util.concurrent;

/// tip

Review what each line does by clicking each number bubble in the code. 👆

///

/// warning

Make sure to **always** use the **exec form** of the `CMD` instruction, as explained below.

///

#### Use `CMD` - Exec Form { #use-cmd-exec-form }

The [`CMD`](https://docs.docker.com/reference/dockerfile/#cmd) Docker instruction can be written using two forms:

✅ **Exec** form:

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

The most common case would be [returning a Response directly as explained later in the advanced docs](../advanced/response-directly.md).

{* ../../docs_src/response_model/tutorial003_02_py310.py hl[8,10:11] *}

 * which contained the following notice:
 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

package com.google.common.util.concurrent;

because the whole sentence was removed from the English text, then also remove the abbr element. The reasoning for this rule is, that such additional abbr elements are manually added by the human editor of the translation, in order to translate or explain an English word to the human readers of the translation. These additional abbr elements would not make sense in the English text, but they do make sense in the translation. So keep them in the translation, even though they are not part of the English...

 *
 * <h3>Additional documentation</h3>
 *
 * <p>See the Guava User Guide for the {@code common.graph} package (<a
 * href="https://github.com/google/guava/wiki/GraphsExplained">"Graphs Explained"</a>) for
 * additional documentation, including:
 *
 * <ul>
 *   <li><a
 *       href="https://github.com/google/guava/wiki/GraphsExplained#equals-hashcode-and-graph-equivalence">

 *
 * <h3>Additional documentation</h3>
 *
 * <p>See the Guava User Guide for the {@code common.graph} package (<a
 * href="https://github.com/google/guava/wiki/GraphsExplained">"Graphs Explained"</a>) for
 * additional documentation, including:
 *
 * <ul>
 *   <li><a
 *       href="https://github.com/google/guava/wiki/GraphsExplained#equals-hashcode-and-graph-equivalence">

**This release upgrades OkHttp to Kotlin.** We tried our best to make fast and safe to upgrade
from OkHttp 3.x. We wrote an [upgrade guide][upgrading_to_okhttp_4] to help with the migration and a
[blog post][okhttp4_blog_post] to explain it.

 *  Fix: Target Java 8 bytecode for Java and Kotlin.


## Version 4.0.0-RC3

_2019-06-24_

 *  Fix: Retain binary-compatibility in `okhttp3.internal.HttpMethod`. Naughty third party SDKs

    return 1 << IntMath.log2(x, RoundingMode.CEILING);
  }

  /*
   * This method was written by Doug Lea with assistance from members of JCP JSR-166 Expert Group
   * and released to the public domain, as explained at
   * http://creativecommons.org/licenses/publicdomain
   *
   * As of 2010/06/11, this method is identical to the (package private) hash method in OpenJDK 7's
   * java.util.HashMap class.
   */