protected ForwardingObject() {}

  /**
   * Returns the backing delegate instance that methods are forwarded to. Abstract subclasses
   * generally override this method with an abstract method that has a more specific return type,
   * such as {@link ForwardingSet#delegate}. Concrete subclasses override this method to supply the
   * instance being decorated.
   */
  protected abstract Object delegate();

  }

  @Override
  public Iterator<E> iterator() {
    if (iterator == null) {
      // TODO: throw something else? Do we worry that people's code and tests
      // might be relying on this particular type of exception?
      throw new IllegalStateException();
    }
    try {
      return iterator;
    } finally {
      iterator = null;
    }
  }

///

## Cabeçalhos duplicados

É possível receber cabeçalhos duplicados. Isso significa, o mesmo cabeçalho com vários valores.

Você pode definir esses casos usando uma lista na declaração de tipo.

Você receberá todos os valores do cabeçalho duplicado como uma `list` Python.

Por exemplo, para declarar um cabeçalho de `X-Token` que pode aparecer mais de uma vez, você pode escrever:

**FastAPI** se encargará de leer esos datos del lugar correcto en lugar de JSON.

/// note | Detalles técnicos

Los datos de forms normalmente se codifican usando el "media type" `application/x-www-form-urlencoded`.

Pero cuando el formulario incluye archivos, se codifica como `multipart/form-data`. Leerás sobre la gestión de archivos en el próximo capítulo.

**FastAPI** will make sure to read that data from the right place instead of JSON.

/// note | Technical Details

Data from forms is normally encoded using the "media type" `application/x-www-form-urlencoded`.

But when the form includes files, it is encoded as `multipart/form-data`. You'll read about handling files in the next chapter.

```json
{
    "detail": [
        {
            "type": "extra_forbidden",
            "loc": ["cookie", "santa_tracker"],
            "msg": "Extra inputs are not permitted",
            "input": "good-list-please"
        }
    ]
}
```

## Заключение

{\n  word-wrap: normal;\n}\nselect:disabled {\n  opacity: 1;\n}\n\n[list]:not([type=date]):not([type=datetime-local]):not([type=month]):not([type=week]):not([type=time])::-webkit-calendar-picker-indicator {\n  display: none !important;\n}\n\nbutton,\n[type=button],\n[type=reset],\n[type=submit] {\n  -webkit-appearance: button;\n}\nbutton:not(:disabled),\n[type=button]:not(:disabled),\n[type=reset]:not(:disabled),\n[type=submit]:not(:disabled) {\n  cursor: pointer;\n}\n\n::-moz-focus-inner {\n  padding:...

package org.apache.maven.artifact.repository;

import java.util.Calendar;
import java.util.Date;

/**
 * Describes a set of policies for a repository to use under certain conditions.
 *
 * @deprecated Avoid use of this type, if you need access to local repository use repository system session instead.
 */
@Deprecated
public class ArtifactRepositoryPolicy {
    public static final String UPDATE_POLICY_NEVER = "never";

```JSON
{
    "detail": [
        {
            "loc": [
                "query",
                "needy"
            ],
            "msg": "field required",
            "type": "value_error.missing"
        }
    ]
}
```

`needy` 🚚 🔢, 👆 🔜 💪 ⚒ ⚫️ 📛:

```
http://127.0.0.1:8000/items/foo-item?needy=sooooneedy
```

...👉 🔜 👷:

```JSON
{

    }

    /**
     * Tests if this input stream supports the mark and reset methods.
     * This method delegates to {@link FileInputStream#markSupported()}.
     *
     * @return {@code true} if this stream type supports the mark and reset method; {@code false} otherwise
     */
    @Override
    public boolean markSupported() {
        return fileInputStream.markSupported();
    }

    /**