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,

 * under the License.
 */
package org.apache.maven.graph;

import java.io.File;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;

import org.apache.maven.MavenExecutionException;
import org.apache.maven.execution.MavenExecutionRequest;
import org.apache.maven.execution.ProjectActivation;

- 代わりに ✨ **`Union[SomeType, None]` を使いましょう** ✨。

どちらも等価で内部的には同一ですが、「optional（任意）」という語が値が任意だと誤解させやすく、実際の意味は「`None` を取り得る」であり、任意ではなく依然として必須である場合でもそうです。そのため `Optional` より `Union` を勧めます。

`Union[SomeType, None]` の方が意味がより明確だと思います。

これは用語や名前付けの話に過ぎませんが、その言葉があなたやチームメイトのコードの捉え方に影響します。

例として次の関数を見てみましょう:

```python
from typing import Optional


def say_hi(name: Optional[str]):
    print(f"Hey {name}!")
```

			Optional:    true,
			Type:        "csv",
		},
		config.HelpKV{
			Key:         AllowEncrypted,
			Description: `enable 'encryption' along with compression`,
			Optional:    true,
			Type:        "on|off",
		},
		config.HelpKV{
			Key:         config.Comment,
			Description: config.DefaultComment,
			Optional:    true,
			Type:        "sentence",
		},
	}

   * @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;
  }

            @Nonnull
            @Override
            public Optional<Source> getInstallationToolchainsSource() {
                return Optional.ofNullable(installationToolchainsSource);
            }

            @Nonnull
            @Override
            public Optional<Source> getUserToolchainsSource() {
                return Optional.ofNullable(userToolchainsSource);
            }

            @Override

    public <T> T lookup(Class<T> type, String name) {
        return null;
    }

    @Override
    public <T> Optional<T> lookupOptional(Class<T> type) {
        return Optional.empty();
    }

    @Override
    public <T> Optional<T> lookupOptional(Class<T> type, String name) {
        return Optional.empty();
    }

    @Override
    public <T> List<T> lookupList(Class<T> type) {
        return List.of();
    }

            .addValue(Collections.emptyMap())
            .addValue(null)
            .add(SHORT_NAME, Optional.of("1"))
            .add(LONG_NAME, Optional.of("1"))
            .add(SHORT_NAME, Optional.absent())
            .add(LONG_NAME, Optional.absent())
            .add(SHORT_NAME, Optional.of("2"))
            .add(SHORT_NAME, Optional.absent())
            .addValue(null)
            .add(SHORT_NAME, new int[] {1})

package org.apache.maven.cling.invoker.cisupport;

import java.util.Optional;

import org.apache.maven.api.cli.cisupport.CIInfo;

/**
 * Circle CI support.
 */
public class CircleCIDetector implements CIDetector {
    public static final String NAME = "CircleCI";

    private static final String CIRCLECI = "CIRCLECI";

    @Override
    public Optional<CIInfo> detectCI() {
        String ciEnv = System.getenv(CIRCLECI);

package org.apache.maven.cling.invoker.cisupport;

import java.util.Optional;

import org.apache.maven.api.cli.cisupport.CIInfo;

/**
 * Jenkins CI support.
 */
public class JenkinsCIDetector implements CIDetector {
    public static final String NAME = "Jenkins";

    private static final String WORKSPACE = "WORKSPACE";

    @Override
    public Optional<CIInfo> detectCI() {
        String workspace = System.getenv(WORKSPACE);