## Follow-up Requests

When your requested URL has moved, the webserver will return a response code like `302` to indicate the document’s new URL. OkHttp will follow the redirect to retrieve a final response.

# Body - Nested Models

With **FastAPI**, you can define, validate, document, and use arbitrarily deeply nested models (thanks to Pydantic).

## List fields

You can define an attribute to be a subtype. For example, a Python `list`:

//// tab | Python 3.10+

```Python hl_lines="12"
{!> ../../docs_src/body_nested_models/tutorial001_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="14"

  @SuppressWarnings({"nullness", "TypeParameterUnusedInFormals", "ReturnMissingNullable"})
  // The warnings are legitimate. Each time we use this method, we document why.
  @ParametricNullness
  static <T extends @Nullable Object> T unsafeNull() {
    return null;
  }

  private NullnessCasts() {}

  @SuppressWarnings({"nullness", "TypeParameterUnusedInFormals", "ReturnMissingNullable"})
  // The warnings are legitimate. Each time we use this method, we document why.
  @ParametricNullness
  static <T extends @Nullable Object> T unsafeNull() {
    return null;
  }

  private NullnessCasts() {}

```

////

O **FastAPI** irá **extrair** as informações para **cada campo** dos **dados do formulário** na requisição e dar para você o modelo Pydantic que você definiu.

## Confira os Documentos

Você pode verificar na UI de documentação em `/docs`:

<div class="screenshot">
<img src="/img/tutorial/request-form-models/image01.png">
</div>

## Proibir Campos Extras de Formulários

   * "plain {@code T}." This API provides that.
   */
  @SuppressWarnings({"nullness", "TypeParameterUnusedInFormals", "ReturnMissingNullable"})
  // The warnings are legitimate. Each time we use this method, we document why.
  @ParametricNullness
  static <T extends @Nullable Object> T uncheckedNull() {
    return null;
  }

  private NullnessCasts() {}

            throw new XmlPullParserException(e.getMessage(), null, e);
        }
    }

    public interface ContentTransformer {
        /**
         * Interpolate the value read from the xpp3 document
         * @param source The source value
         * @param fieldName A description of the field being interpolated. The implementation may use this to
         *                           log stuff.

	if len(r) == 0 {
		return "", false
	}
	return string(r[1:]), true
}

func evalSQLSubstring(s string, startIdx, length int) (res string, err error) {
	rs := []rune(s)

	// According to s3 document, if startIdx < 1, it is set to 1.
	if startIdx < 1 {
		startIdx = 1
	}

	if startIdx > len(rs) {
		startIdx = len(rs) + 1
	}

	// StartIdx is 1-based in the input
	startIdx--

// Standard path where an app would find cross domain policy information.
const crossDomainXMLEntity = "/crossdomain.xml"

// A cross-domain policy file is an XML document that grants a web client, such as Adobe Flash Player
// or Adobe Acrobat (though not necessarily limited to these), permission to handle data across domains.

        return super.read(in);
    }

    public interface ContentTransformer {
        /**
         * Interpolate the value read from the xpp3 document
         *
         * @param source    the source value
         * @param fieldName a description of the field being interpolated. The implementation may use this to
         *                  log stuff