```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009_py39.py!}
```

O uso de `Optional[str]` em vez de apenas `str` permitirá que o editor o ajude a detectar erros, onde você pode estar assumindo que um valor é sempre um `str`, quando na verdade também pode ser `None`.

```

////

#### Uso de `Union` u `Optional` { #using-union-or-optional }

Si estás usando una versión de Python inferior a 3.10, aquí tienes un consejo desde mi punto de vista muy **subjetivo**:

* 🚨 Evita usar `Optional[SomeType]`
* En su lugar ✨ **usa `Union[SomeType, None]`** ✨.

        void shouldBeApplicableWhenModelOptionTrue() {
            UpgradeOptions options = mock(UpgradeOptions.class);
            when(options.model()).thenReturn(Optional.of(true));
            when(options.all()).thenReturn(Optional.empty());

            UpgradeContext context = createMockContext(options);

            assertTrue(strategy.isApplicable(context), "Strategy should be applicable when --model is true");

from typing import Optional

from fastapi import Depends, FastAPI, Security
from fastapi.security.open_id_connect_url import OpenIdConnect
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

oid = OpenIdConnect(openIdConnectUrl="/openid", auto_error=False)


class User(BaseModel):
    username: str


def get_current_user(oauth_header: Optional[str] = Security(oid)):
    if oauth_header is None:

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

import java.util.Optional;

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

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

    private static final String TEAMCITY_VERSION = "TEAMCITY_VERSION";

    @Override
    public Optional<CIInfo> detectCI() {

import org.codelibs.fess.util.ComponentUtil;
import org.codelibs.fess.util.DocumentUtil;
import org.codelibs.fess.util.FacetResponse;
import org.dbflute.optional.OptionalEntity;
import org.dbflute.optional.OptionalThing;
import org.lastaflute.web.util.LaRequestUtil;
import org.opensearch.action.search.SearchRequestBuilder;
import org.opensearch.action.search.SearchResponse;

 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.execution;

import java.util.Optional;

import org.apache.maven.lifecycle.LifecycleExecutionException;
import org.apache.maven.model.Dependency;
import org.apache.maven.project.MavenProject;
import org.junit.jupiter.api.BeforeEach;

   */
  RangeSet<C> complement();

  /**
   * Returns a view of the intersection of this {@code RangeSet} with the specified range.
   *
   * <p>The returned view supports all optional operations supported by this {@code RangeSet}, with
   * the caveat that an {@link IllegalArgumentException} is thrown on an attempt to {@linkplain

  <dependencies>
    <dependency>
      <groupId>maven-test</groupId>
      <artifactId>t05-d</artifactId>
      <version>1.1</version>
      <type>jar</type>
      <scope>compile</scope>
      <optional>true</optional>
    </dependency>
  </dependencies>

  <dependencies>
    <dependency>
      <groupId>maven-test</groupId>
      <artifactId>t08-d</artifactId>
      <version>1.1</version>
      <type>jar</type>
      <scope>compile</scope>
      <optional>true</optional>
    </dependency>
  </dependencies>