Cuando instalas FastAPI con `pip install "fastapi[standard]"` viene con el grupo `standard` de dependencias opcionales:

Usadas por Pydantic:

* [`email-validator`](https://github.com/JoshData/python-email-validator) - para validación de correos electrónicos.

Usadas por Starlette:

* [`httpx`](https://www.python-httpx.org) - Requerido si deseas usar el `TestClient`.

Quando você instala o FastAPI com `pip install "fastapi[standard]"`, ele vem com o grupo `standard` de dependências opcionais:

Utilizado pelo Pydantic:

* [`email-validator`](https://github.com/JoshData/python-email-validator) - para validação de email.

Utilizado pelo Starlette:

* [`httpx`](https://www.python-httpx.org) - Obrigatório caso você queira utilizar o `TestClient`.

        } finally {
            Thread.currentThread().setContextClassLoader(oldCL);
            System.setProperties(oldProps);
        }
    }

    protected int doInvoke(C context) throws Exception {
        validate(context);
        pushCoreProperties(context);
        pushUserProperties(context);
        setupGuiceClassLoading(context);
        configureLogging(context);
        createTerminal(context);

        // phase 1
        DefaultModelBuildingResult result = new DefaultModelBuildingResult();

        DefaultModelProblemCollector problems = new DefaultModelProblemCollector(result);

        // read and validate raw model
        Model inputModel = request.getRawModel();
        if (inputModel == null) {
            inputModel = readModel(request.getModelSource(), request.getPomFile(), request, problems);
        }

* **Extensible**:
    * Pydantic permite definir tipos de datos personalizados o puedes extender la validación con métodos en un modelo decorados con el decorador validator.

	if !owner {
		return errAuthentication
	}

	return nil
}

// Authenticates storage client's requests and validates for skewed time.
func storageServerRequestValidate(r *http.Request) error {
	token, err := jwtreq.AuthorizationHeaderExtractor.ExtractToken(r)
	if err != nil {
		if err == jwtreq.ErrNoTokenInRequest {

`Annotated` 안에서 [Pydantic의 `AfterValidator`](https://docs.pydantic.dev/latest/concepts/validators/#field-after-validator)를 사용하면 이를 구현할 수 있습니다.

/// tip | 팁

Pydantic에는 [BeforeValidator](https://docs.pydantic.dev/latest/concepts/validators/#field-before-validator)와 같은 다른 것들도 있습니다. 🤓

///

		return entries, err
	}

	// Marker points to before the prefix, just ignore it.
	if o.Marker < o.Prefix {
		o.Marker = ""
	}

	// Marker is set validate pre-condition.
	if o.Marker != "" && o.Prefix != "" {
		// Marker not common with prefix is not implemented. Send an empty response
		if !HasPrefix(o.Marker, o.Prefix) {
			return entries, io.EOF
		}
	}

                this.pathTypeFilter = (pathTypeFilter != null) ? pathTypeFilter : DEFAULT_FILTER;
                this.targetVersion = targetVersion;
                this.repositories = validate(repositories);
                if (verbose && requestType != RequestType.COLLECT) {
                    throw new IllegalArgumentException("verbose cannot only be true when collecting dependencies");
                }

        if not errors:
            # Shared serializer for stream items (JSONL and SSE).
            # Validates against stream_item_field when set, then
            # serializes to JSON bytes.
            def _serialize_data(data: Any) -> bytes:
                if stream_item_field:
                    value, errors_ = stream_item_field.validate(
                        data, {}, loc=("response",)
                    )