Por ejemplo, el modelo anterior declara un “`object`” JSON (o `dict` en Python) como:

```JSON
{
    "name": "Foo",
    "description": "An optional description",
    "price": 45.2,
    "tax": 3.5
}
```

...dado que `description` y `tax` son opcionales (con un valor por defecto de `None`), este “`object`” JSON también sería válido:

```JSON
{
    "name": "Foo",
    "price": 45.2
}
```

    * **WebSockets**
    * extremely easy tests based on HTTPX and `pytest`
    * **CORS**
    * **Cookie Sessions**
    * ...and more.

### Deploy your app (optional)

You can optionally deploy your FastAPI app to <a href="https://fastapicloud.com" class="external-link" target="_blank">FastAPI Cloud</a>, go and join the waiting list if you haven't. 🚀

            .add("field11", Arrays.asList("Hello"))
            .add("field12", new ArrayList<>())
            .add("field13", new HashMap<>())
            // Optionals
            .add("field26", Optional.of("World"))
            .add("field27", Optional.absent())
            // Arrays
            .add("field31", new Object[] {"!!!"})
            .add("field32", new boolean[0])
            .add("field33", new byte[0])

    exclusiveMaximum: Optional[float] = None
    minimum: Optional[float] = None
    exclusiveMinimum: Optional[float] = None
    maxLength: Optional[int] = Field(default=None, ge=0)
    minLength: Optional[int] = Field(default=None, ge=0)
    pattern: Optional[str] = None
    maxItems: Optional[int] = Field(default=None, ge=0)
    minItems: Optional[int] = Field(default=None, ge=0)
    uniqueItems: Optional[bool] = None

	ServerSideHasher         hash.Hash
	ServerSideChecksumResult *Checksum

	trailer http.Header

	sha256 hash.Hash
}

// Options are optional arguments to NewReaderWithOpts, Options
// simply converts positional arguments to NewReader() into a
// more flexible way to provide optional inputs. This is currently
// used by the FanOut API call mostly to disable expensive md5sum
// calculation repeatedly under hash.Reader.

    p: Optional[str] = None


@app.get("/model-optional-str")
async def read_model_optional_str(p: Annotated[CookieModelOptionalStr, Cookie()]):
    return {"p": p.p}


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)
def test_optional_str_schema(path: str):
    assert app.openapi()["paths"][path]["get"]["parameters"] == [
        {
            "required": False,

class HeaderModelOptionalListStr(BaseModel):
    p: Optional[list[str]] = None


@app.get("/model-optional-list-str")
async def read_model_optional_list_str(
    p: Annotated[HeaderModelOptionalListStr, Header()],
):
    return {"p": p.p}


@pytest.mark.parametrize(
    "path",
    ["/optional-list-str", "/model-optional-list-str"],
)
def test_optional_list_str_schema(path: str):

queue_dir      (path)      staging dir for undelivered messages e.g. '/home/events'
queue_limit    (number)    maximum limit for undelivered messages, defaults to '100000'
comment        (sentence)  optionally add a comment to this setting
```

Or environment variables

```
KEY:
notify_amqp[:name]  publish bucket notifications to AMQP endpoints

ARGS:

            return Optional.of(Boolean.TRUE);
        }
        return Optional.empty();
    }

    @Override
    public Optional<Boolean> updateSnapshots() {
        if (commandLine.hasOption(CLIManager.UPDATE_SNAPSHOTS)) {
            return Optional.of(Boolean.TRUE);
        }
        return Optional.empty();
    }

    @Override
    public Optional<List<String>> activatedProfiles() {

):
    return {"p": p}


class FormModelOptionalListStr(BaseModel):
    p: Optional[list[str]] = None


@app.post("/model-optional-list-str", operation_id="model_optional_list_str")
async def read_model_optional_list_str(p: Annotated[FormModelOptionalListStr, Form()]):
    return {"p": p.p}


@pytest.mark.parametrize(
    "path",