* `skip=20`: because you set it in the URL
* `limit=10`: because that was the default value

## Optional parameters { #optional-parameters }

The same way, you can declare optional query parameters, by setting their default to `None`:

{* ../../docs_src/query_params/tutorial002_py310.py hl[7] *}

In this case, the function parameter `q` will be optional, and will be `None` by default.

/// check

   * Point ::= SEQUENCE {
   *   x [0] INTEGER OPTIONAL,
   *   y [1] INTEGER OPTIONAL
   * }
   * ```
   *
   * You may also specify a tag class like [DerHeader.TAG_CLASS_APPLICATION]. The default tag class
   * is [DerHeader.TAG_CLASS_CONTEXT_SPECIFIC].
   *
   * ```
   * Point ::= SEQUENCE {
   *   x [APPLICATION 0] INTEGER OPTIONAL,
   *   y [APPLICATION 1] INTEGER OPTIONAL
   * }
   * ```
   */
  fun withTag(

from typing import Optional

from fastapi import FastAPI
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()


class SubModel(BaseModel):
    a: Optional[str] = "foo"


class Model(BaseModel):
    x: Optional[int] = None
    sub: SubModel


class ModelSubclass(Model):
    y: int
    z: int = 0
    w: Optional[int] = None


class ModelDefaults(BaseModel):

   *
   * <p><b>Java 9 users:</b> use {@code optional.stream()} instead.
   */
  @Beta
  @InlineMe(replacement = "optional.stream()")
  @InlineMeValidationDisabled("Java 9+ API only")
  public static <T> Stream<T> stream(java.util.Optional<T> optional) {
    return optional.isPresent() ? Stream.of(optional.get()) : Stream.empty();
  }

  /**
   * If a value is present in {@code optional}, returns a stream containing only that element,

```

////

#### Using `Union` or `Optional` { #using-union-or-optional }

If you are using a Python version below 3.10, here's a tip from my very **subjective** point of view:

* 🚨 Avoid using `Optional[SomeType]`
* Instead ✨ **use `Union[SomeType, None]`** ✨.

   * @throws NullPointerException if any element in the stream is {@code null}.
   * @return {@code Optional.of(onlyElement)} if the stream has exactly one element (must not be
   *     {@code null}) and returns {@code Optional.empty()} if it has none.
   */
  @SuppressWarnings("unchecked")
  public static <T> Collector<T, ?, Optional<T>> toOptional() {
    return (Collector) TO_OPTIONAL;
  }

			Optional:    true,
			Type:        "path",
			Sensitive:   true,
		},
		config.HelpKV{
			Key:         ClientCertKey,
			Description: `client cert key for mTLS authentication` + defaultHelpPostfix(ClientCertKey),
			Optional:    true,
			Type:        "path",
			Sensitive:   true,
		},
		config.HelpKV{
			Key:         config.Comment,
			Description: config.DefaultComment,
			Optional:    true,

			Description: `name for the site e.g. "cal-rack0"`,
			Optional:    true,
		},
		HelpKV{
			Key:         RegionKey,
			Type:        "string",
			Description: `name of the location of the server e.g. "us-west-1"`,
			Optional:    true,
		},
		HelpKV{
			Key:         Comment,
			Type:        "sentence",
			Description: DefaultComment,
			Optional:    true,
		},
	}

	RegionHelp = HelpKVS{
		HelpKV{

            ),
        ],
        scheme_name: Annotated[
            Optional[str],
            Doc(
                """
                Security scheme name.

                It will be included in the generated OpenAPI (e.g. visible at `/docs`).
                """
            ),
        ] = None,
        description: Annotated[
            Optional[str],
            Doc(
                """

    }

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

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