- 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}!")
```

        // v1 == 0.
        .optional(defaultValue = 0),
      Adapters.INTEGER_AS_BIG_INTEGER,
      algorithmIdentifier,
      name,
      validity,
      name,
      subjectPublicKeyInfo,
      Adapters.BIT_STRING.withTag(tag = 1L).optional(),
      Adapters.BIT_STRING.withTag(tag = 2L).optional(),
      extension.asSequenceOf().withExplicitBox(tag = 3).optional(defaultValue = listOf()),
      decompose = {

     * @param active Should the profile be activated?
     * @param optional Can the build continue if the profile does not exist?
     */
    public void addProfileActivation(String id, boolean active, boolean optional) {
        final ActivationSettings settings = ActivationSettings.of(active, optional);
        this.activations.put(id, settings);
    }

     * @param active Should the project be activated?
     * @param optional Can the build continue if the project does not exist?
     */
    public void addProjectActivation(String selector, boolean active, boolean optional) {
        final ActivationSettings settings = ActivationSettings.of(active, optional);
        this.activations.add(new ProjectActivationSettings(selector, settings));
    }

    /**
     * Performs a lookup for optional typed component.
     *
     * @param type The component type.
     * @return Optional carrying component or empty optional if no such component.
     * @param <T> The component type.
     * @throws LookupException if there is some provisioning related issue.
     */
    @Nonnull
    <T> Optional<T> lookupOptional(Class<T> type);

    /**

 * 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;

        }
        return Optional.empty();
    }

    @Override
    @Nonnull
    public Optional<String> modelVersion() {
        if (commandLine.hasOption(CLIManager.MODEL_VERSION)) {
            return Optional.of(commandLine.getOptionValue(CLIManager.MODEL_VERSION));
        }
        return Optional.empty();
    }

    @Override
    @Nonnull
    public Optional<String> directory() {

    private ProtoLookup(Map<Class<?>, Object> components) {
        this.components = components;
    }

    @Override
    public <T> T lookup(Class<T> type) {
        Optional<T> optional = lookupOptional(type);
        if (optional.isPresent()) {
            return optional.get();
        } else {
            throw new LookupException("No mapping for key: " + type.getName());
        }
    }

    @Override

    "com.oracle.svm.core.annotate;resolution:=optional," +
    "com.oracle.svm.core.configure;resolution:=optional," +
    "dalvik.system;resolution:=optional," +
    "org.conscrypt;resolution:=optional," +
    "org.bouncycastle.*;resolution:=optional," +
    "org.openjsse.*;resolution:=optional," +
    "org.graalvm.nativeimage;resolution:=optional," +
    "org.graalvm.nativeimage.hosted;resolution:=optional," +

@REM
@REM   JAVA_HOME           (Optional) Points to a Java installation.
@REM   MAVEN_BATCH_ECHO    (Optional) Set to 'on' to enable the echoing of the batch commands.
@REM   MAVEN_BATCH_PAUSE   (Optional) set to 'on' to wait for a key stroke before ending.
@REM   MAVEN_OPTS          (Optional) Java runtime options used when Maven is executed.
@REM   MAVEN_SKIP_RC       (Optional) Flag to disable loading of mavenrc files.