* Créer un répertoire `app` et y entrer.
* Créez un fichier `main.py` avec :

```Python
from typing import Optional

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Optional[str] = None):
    return {"item_id": item_id, "q": q}
```

  assertEquals("hello, world!", chat.messages());

  chat.loadMore();
  chat.loadMore();
  assertEquals(""
      + "hello, world!\n"
      + "sup, bra?\n"
      + "yo dog", chat.messages());

  // Optional: confirm that your app made the HTTP requests you were expecting.
  RecordedRequest request1 = server.takeRequest();
  assertEquals("/v1/chat/messages/", request1.getUrl().encodedPath());

    assertNotNull(ArbitraryInstances.get(Object.class));
    assertEquals(0, ArbitraryInstances.get(Number.class));
    assertEquals(UTF_8, ArbitraryInstances.get(Charset.class));
    assertEquals(Optional.empty(), ArbitraryInstances.get(Optional.class));
    assertEquals(OptionalInt.empty(), ArbitraryInstances.get(OptionalInt.class));
    assertEquals(OptionalLong.empty(), ArbitraryInstances.get(OptionalLong.class));

import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.List;
import java.util.Set;

/**
 * Optional features of classes derived from {@code List}.
 *
 * @author George van den Driessche
 */
@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible

import com.google.common.collect.testing.features.TesterAnnotation;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Set;

/**
 * Optional features of classes derived from {@code Multimap}.
 *
 * @author Louis Wasserman
 */
@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible

        return artifact.isSelectedVersionKnown();
    }

    /** {@inheritDoc} */
    @Override
    public void setOptional(boolean optional) {
        artifact.setOptional(optional);
    }

    /** {@inheritDoc} */
    @Override
    public int hashCode() {
        int result = 17;

        result = 37 * result + getGroupId().hashCode();

     * Required field with maximum length of 100 characters.
     */
    @Required
    @Size(max = 100)
    public String name;

    /**
     * The version of the plugin to delete.
     * Optional field with maximum length of 100 characters.
     */
    @Size(max = 100)
    public String version;

import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Set;

/**
 * Optional features of classes derived from {@code Set}.
 *
 * @author George van den Driessche
 */
@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible

import java.util.Locale;

import org.codelibs.fess.opensearch.config.bsentity.BsCrawlingInfoParam;
import org.codelibs.fess.opensearch.config.exbhv.CrawlingInfoBhv;
import org.codelibs.fess.util.ComponentUtil;
import org.dbflute.optional.OptionalEntity;

/**
 * @author ESFlute (using FreeGen)
 */
public class CrawlingInfoParam extends BsCrawlingInfoParam {

    private static final long serialVersionUID = 1L;

* 変数`prices`は`dict`であり:
    * この`dict`のキーは`str`型です。（つまり、各項目の名前）
    * この`dict`の値は`float`型です。（つまり、各項目の価格）

#### `Optional`

また、`Optional`を使用して、変数が`str`のような型を持つことを宣言することもできますが、それは「オプション」であり、`None`にすることもできます。

```Python hl_lines="1 4"
{!../../docs_src/python_types/tutorial009.py!}
```

ただの`str`の代わりに`Optional[str]`を使用することで、エディタは値が常に`str`であると仮定している場合に実際には`None`である可能性があるエラーを検出するのに役立ちます。

#### ジェネリック型