static {
        // Those two public constants are initialized here, as they need all the private constants
        // above to be initialized first, but the code style imposes the public constants to be
        // defined above the private ones...
        OS_FAMILY = getOsFamily();
        IS_WINDOWS = isFamily(FAMILY_WINDOWS);
    }

    private Os() {}

    /**

    return UsingToStringOrdering.INSTANCE;
  }

  /**
   * Returns an arbitrary ordering over all objects, for which {@code compare(a, b) == 0} implies
   * {@code a == b} (identity equality). There is no meaning whatsoever to the order imposed, but it
   * is constant for the life of the VM.
   *
   * <p>Because the ordering is identity-based, it is not "consistent with {@link

   * a {@code Future} is returned to the caller (unless the executor has been shutdown).
   *
   * <p>Although all tasks are immediately executed in the thread that submitted the task, this
   * {@code ExecutorService} imposes a small locking overhead on each task submission in order to
   * implement shutdown and termination behavior.
   *
   * <p>The implementation deviates from the {@code ExecutorService} specification with regards to

   * {@link Cache#stats} will return zero for all statistics. Note that recording stats requires
   * bookkeeping to be performed with each operation, and thus imposes a performance penalty on
   * cache operation.
   *
   * @return this {@code CacheBuilder} instance (for chaining)
   * @since 12.0 (previously, stats collection was automatic)
   */
  @CanIgnoreReturnValue

      message = "Moved to extension function. Put the 'content' argument first to fix Java",
      replaceWith =
        ReplaceWith(
          expression = "content.toRequestBody(contentType)",
          imports = ["okhttp3.RequestBody.Companion.toRequestBody"],
        ),
      level = DeprecationLevel.WARNING,
    )
    fun create(
      contentType: MediaType?,
      content: String,

{* ../../docs_src/bigger_applications/app_an_py39/routers/items.py hl[3] title["app/routers/items.py"] *}

#### How relative imports work { #how-relative-imports-work }

/// tip

If you know perfectly how imports work, continue to the next section below.

///

A single dot `.`, like in:

```Python
from .dependencies import get_token_header
```

would mean:

   * @deprecated Prefer {@code asCharSource(file, charset).read()}.
   */
  @Deprecated
  @InlineMe(
      replacement = "Files.asCharSource(file, charset).read()",
      imports = "com.google.common.io.Files")
  public static String toString(File file, Charset charset) throws IOException {
    return asCharSource(file, charset).read();
  }

  /**

///

## `HTTPSRedirectMiddleware` { #httpsredirectmiddleware }

Impone que todas las requests entrantes deben ser `https` o `wss`.

Cualquier request entrante a `http` o `ws` será redirigida al esquema seguro.

{* ../../docs_src/advanced_middleware/tutorial001_py39.py hl[2,6] *}

## `TrustedHostMiddleware` { #trustedhostmiddleware }

{* ../../docs_src/bigger_applications/app_an_py39/routers/items.py hl[3] title["app/routers/items.py"] *}

#### Cómo funcionan los imports relativos { #how-relative-imports-work }

/// tip | Consejo

Si sabes perfectamente cómo funcionan los imports, continúa a la siguiente sección.

///

Un solo punto `.`, como en:

```Python
from .dependencies import get_token_header
```

Desde FastAPI 0.119.0, también hay compatibilidad parcial para Pydantic v1 desde dentro de Pydantic v2, para facilitar la migración a v2.

Así que podrías actualizar Pydantic a la última versión 2 y cambiar los imports para usar el submódulo `pydantic.v1`, y en muchos casos simplemente funcionaría.

{* ../../docs_src/pydantic_v1_in_v2/tutorial002_an_py310.py hl[2,5,15] *}

/// warning | Advertencia