[
        ("/items", None, 200, {"ads_id": None}),
        ("/items", {"ads_id": "ads_track"}, 200, {"ads_id": "ads_track"}),
        (
            "/items",
            {"ads_id": "ads_track", "session": "cookiesession"},
            200,
            {"ads_id": "ads_track"},
        ),
        ("/items", {"session": "cookiesession"}, 200, {"ads_id": None}),
    ],
)

👯‍♂️ 💼 👉 ⛓ 👈 `item` 💪 `int` ⚖️ `str`.

#### 🎲 `None`

👆 💪 📣 👈 💲 💪 ✔️ 🆎, 💖 `str`, ✋️ 👈 ⚫️ 💪 `None`.

🐍 3️⃣.6️⃣ & 🔛 (✅ 🐍 3️⃣.1️⃣0️⃣) 👆 💪 📣 ⚫️ 🏭 & ⚙️ `Optional` ⚪️➡️ `typing` 🕹.

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

⚙️ `Optional[str]` ↩️ `str` 🔜 ➡️ 👨‍🎨 ℹ 👆 🔍 ❌ 🌐❔ 👆 💪 🤔 👈 💲 🕧 `str`, 🕐❔ ⚫️ 💪 🤙 `None` 💁‍♂️.

    rules:
      - apiGroups:
          - ""
        apiVersions:
          - v1
        operations:
          - CREATE
        resources:
          - pods
        scope: '*'
    sideEffects: None
    timeoutSeconds: 10
  - admissionReviewVersions:
      - v1beta1
      - v1
    clientConfig:
      service:
        name: istiod-1-16
        namespace: istio-system
        path: /inject

0 1px 0 #fff;\n  opacity: .5;\n}\n\n.close:hover {\n  color: #000;\n  text-decoration: none;\n}\n\n.close:not(:disabled):not(.disabled):hover, .close:not(:disabled):not(.disabled):focus {\n  opacity: .75;\n}\n\nbutton.close {\n  padding: 0;\n  background-color: transparent;\n  border: 0;\n  -webkit-appearance: none;\n  -moz-appearance: none;\n  appearance: none;\n}\n\na.close.disabled {\n  pointer-events: none;\n}\n\n.toast {\n  max-width: 350px;\n  overflow: hidden;\n  font-size: 0.875rem;\n  background-color:...

    [
        ("/items", None, 200, {"ads_id": None}),
        ("/items", {"ads_id": "ads_track"}, 200, {"ads_id": "ads_track"}),
        (
            "/items",
            {"ads_id": "ads_track", "session": "cookiesession"},
            200,
            {"ads_id": "ads_track"},
        ),
        ("/items", {"session": "cookiesession"}, 200, {"ads_id": None}),
    ],
)

app = FastAPI()


def _get_client_key(client_id: str = Query(...)) -> str:
    return f"{client_id}_key"


def _get_client_tag(client_id: Optional[str] = Query(None)) -> Optional[str]:
    if client_id is None:
        return None
    return f"{client_id}_tag"


@app.get("/foo")
def foo_handler(
    client_key: str = Depends(_get_client_key),
    client_tag: Optional[str] = Depends(_get_client_tag),
):

    response = client.get("/users/")
    assert response.status_code == 200, response.text
    assert response.json() == {
        "message": "Hello Users!",
        "params": {"q": None, "skip": 5, "limit": 10},
    }


@needs_py310
def test_override_in_users_with_q():
    from docs_src.dependency_testing.tutorial001_an_py310 import client

    response = client.get("/users/?q=foo")

    response = client.get("/users/")
    assert response.status_code == 200, response.text
    assert response.json() == {
        "message": "Hello Users!",
        "params": {"q": None, "skip": 5, "limit": 10},
    }


@needs_py39
def test_override_in_users_with_q():
    from docs_src.dependency_testing.tutorial001_an_py39 import client

    response = client.get("/users/?q=foo")

    assertSame(CharMatcher.any(), CharMatcher.none().negate());
    assertSame(CharMatcher.none(), CharMatcher.any().negate());

    assertSame(WHATEVER, CharMatcher.any().and(WHATEVER));
    assertSame(CharMatcher.any(), CharMatcher.any().or(WHATEVER));

    assertSame(CharMatcher.none(), CharMatcher.none().and(WHATEVER));
    assertSame(WHATEVER, CharMatcher.none().or(WHATEVER));
  }

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


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


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


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):