annotation: Optional[Any] = None,
        alias: Optional[str] = None,
        alias_priority: Union[int, None] = _Unset,
        # TODO: update when deprecating Pydantic v1, import these types
        # validation_alias: str | AliasPath | AliasChoices | None
        validation_alias: Union[str, None] = None,
        serialization_alias: Union[str, None] = None,
        title: Optional[str] = None,

Commençons avec cette application pour exemple :

{* ../../docs_src/query_params_str_validations/tutorial001.py hl[9] *}

Le paramètre de requête `q` a pour type `Union[str, None]` (ou `str | None` en Python 3.10), signifiant qu'il est de type `str` mais pourrait aussi être égal à `None`, et bien sûr, la valeur par défaut est `None`, donc **FastAPI** saura qu'il n'est pas requis.

/// note

	"sync/atomic"
	"unicode/utf16"
)

// ValueType - defines the type of each JSON value
type ValueType int

// Different types of JSON value
const (
	Unknown ValueType = iota
	Null
	String
	Number
	Boolean
	Array
	Object
)

// MetaValue wraps a decoded interface value with the document
// position and depth at which the value was parsed
type MetaValue struct {
	Offset    int
	Length    int
	Depth     int

  /*
   * This class is used to serialize all ImmutableSortedSet instances,
   * regardless of implementation type. It captures their "logical contents"
   * only. This is necessary to ensure that the existence of a particular
   * implementation type is an implementation detail.
   */
  @J2ktIncompatible // serialization
  private static class SerializedForm<E> implements Serializable {

#include <string>
#include <utility>

#include "absl/memory/memory.h"
#include "absl/status/status.h"
#include "absl/strings/str_cat.h"
#include "absl/types/optional.h"
#include "absl/types/span.h"
#include "tensorflow/c/eager/c_api.h"
#include "tensorflow/c/eager/c_api_experimental.h"
#include "tensorflow/c/eager/immediate_execution_tensor_handle.h"

 *
 * <p>Implementations of this interface are expected to be thread-safe, and can be safely accessed
 * by multiple concurrent threads.
 *
 * @param <K> the type of the cache's keys, which are not permitted to be null
 * @param <V> the type of the cache's values, which are not permitted to be null
 * @author Charles Fry
 * @since 10.0
 */
@DoNotMock("Use CacheBuilder.newBuilder().build()")
@GwtCompatible

```JSON
{
  "detail": [
    {
      "type": "int_parsing",
      "loc": [
        "path",
        "item_id"
      ],
      "msg": "Input should be a valid integer, unable to parse string as an integer",
      "input": "foo",

    val keyPair: KeyPair = heldCertificate.keyPair()
  }

  @Test @Disabled
  fun mediaType() {
    val mediaType: MediaType = MediaType.get("")
    val type: String = mediaType.type()
    val subtype: String = mediaType.subtype()
    val parse: MediaType? = MediaType.parse("")
  }

  @Test @Disabled
  fun mockResponse() {
    val mockResponse = MockResponse()

#define TENSORFLOW_C_EAGER_IMMEDIATE_EXECUTION_TENSOR_HANDLE_H_

#include "tensorflow/c/eager/abstract_tensor_handle.h"
#include "tensorflow/c/tensor_interface.h"
#include "tensorflow/core/framework/types.pb.h"
#include "tensorflow/core/platform/status.h"

namespace tensorflow {

// Abstract interface to a TensorHandle.
//
// A TensorHandle is management class around a Tensor which may track additional

///

```Python hl_lines="19"
{!> ../../docs_src/dependencies/tutorial003.py!}
```

////

But declaring the type is encouraged as that way your editor will know what will be passed as the parameter `commons`, and then it can help you with code completion, type checks, etc:

<img src="/img/tutorial/dependencies/image02.png">

## Shortcut