`Optional[Something]` is actually a shortcut for `Union[Something, None]`, they are equivalent.

This also means that in Python 3.10, you can use `Something | None`:

//// tab | Python 3.10+

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}
```

////

If you have a new feature idea, please build it in an external library. There are
[many libraries][works_with_okhttp] that sit on top or hook in via existing APIs. If you build
something that integrates with OkHttp, tell us so that we can link it!

Before code can be accepted all contributors must complete our
[Individual Contributor License Agreement (CLA)][cla].


Code Contributions

If you have a new feature idea, please build it in an external library. There are
[many libraries][works_with_okhttp] that sit on top or hook in via existing APIs. If you build
something that integrates with OkHttp, tell us so that we can link it!

Before code can be accepted all contributors must complete our
[Individual Contributor License Agreement (CLA)][cla].


Code Contributions

しかし、依存関係を定義する方法はそれだけではありません（その方が一般的かもしれませんが）。

重要なのは、依存関係が「呼び出し可能」なものであることです。

Pythonにおける「**呼び出し可能**」とは、Pythonが関数のように「呼び出す」ことができるものを指します。

そのため、`something`オブジェクト（関数ではないかもしれませんが）を持っていて、それを次のように「呼び出す」（実行する）ことができるとします:

```Python
something()
```

または

```Python
something(some_argument, some_keyword_argument="foo")
```

これを「呼び出し可能」なものと呼びます。

## 依存関係としてのクラス

Pythonのクラスのインスタンスを作成する際に、同じ構文を使用していることに気づくかもしれません。

  @BeforeEach
  fun setUp() {
    originalDefault = TimeZone.getDefault()
    // The default timezone should affect none of these tests: HTTP specified GMT, so we set it to
    // something else.
    TimeZone.setDefault(TimeZone.getTimeZone("America/Los_Angeles"))
  }

  @AfterEach
  @Throws(Exception::class)
  fun tearDown() {
    TimeZone.setDefault(originalDefault)
  }

  @Test

		},
		{
			name: "net.Error",
			err:  &url.Error{Op: "PUT", URL: "http://localhost/1234", Err: restError("remote server offline")},
			want: true,
		},
		{
			name: "net.Error-unmatched",
			err:  errors.New("something"),
			want: false,
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Wrap error
			n := &NetworkError{
				Err: tt.err,
			}
			//nolint:gocritic
			if tt.target == nil {

    * An example is `404`, for a "Not Found" response.
    * For generic errors from the client, you can just use `400`.
* `500` and above are for server errors. You almost never use them directly. When something goes wrong at some part in your application code, or server, it will automatically return one of these status codes.

/// tip

 *   <li><b>Convenience methods:</b> These are implementations of common operations that are
 *       typically implemented by opening a stream using one of the methods in the first category,
 *       doing something and finally closing the stream or channel that was opened.
 * </ul>
 *
 * @since 14.0
 * @author Colin Decker
 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault

      // The JELLY_BEAN field doesn't exist because we're running on a version before Jelly Bean :)
      return new ThrowingCreator();
    } catch (ClassNotFoundException e) {
      // Should be impossible, but we want to return *something* so that class init succeeds.
      return new ThrowingCreator();
    } catch (IllegalAccessException e) {
      // ditto
      return new ThrowingCreator();
    }

# About HTTPS

It is easy to assume that HTTPS is something that is just "enabled" or not.

But it is way more complex than that.

/// tip

If you are in a hurry or don't care, continue with the next sections for step by step instructions to set everything up with different techniques.

///