```

////

#### ⚙️ `Union` ⚖️ `Optional`

🚥 👆 ⚙️ 🐍 ⏬ 🔛 3️⃣.1️⃣0️⃣, 📥 💁‍♂ ⚪️➡️ 👇 📶 **🤔** ☝ 🎑:

* 👶 ❎ ⚙️ `Optional[SomeType]`
* ↩️ 👶 **⚙️ `Union[SomeType, None]`** 👶.

👯‍♂️ 🌓 & 🔘 👫 🎏, ✋️ 👤 🔜 👍 `Union` ↩️ `Optional` ↩️ 🔤 "**📦**" 🔜 😑 🔑 👈 💲 📦, & ⚫️ 🤙 ⛓ "⚫️ 💪 `None`", 🚥 ⚫️ 🚫 📦 & ✔.

👤 💭 `Union[SomeType, None]` 🌖 🔑 🔃 ⚫️❔ ⚫️ ⛓.

from typing import Union

from fastapi import Body, FastAPI, status
from fastapi.responses import JSONResponse

app = FastAPI()

items = {"foo": {"name": "Fighters", "size": 6}, "bar": {"name": "Tenders", "size": 3}}


@app.put("/items/{item_id}")
async def upsert_item(
    item_id: str,
    name: Union[str, None] = Body(default=None),
    size: Union[int, None] = Body(default=None),
):
    if item_id in items:

		case "s": // set
			v, err := strconv.ParseInt(kv[1], 10, 64)
			if err != nil {
				o.ID = mustGetUUID()
				o.Create = true
				continue
			}
			o.set = int(v)
		default:
			// Ignore unknown
		}
	}
}

// encodeMarker will encode a uuid and return it as a marker.
// uuid cannot contain '[', ':' or ','.
func (o listPathOptions) encodeMarker(marker string) string {
	if o.ID == "" {

func getFSType(ftype int32) string {
	fsTypeHex := strconv.FormatInt(int64(ftype), 16)
	fsTypeString, ok := fsType2StringMap[fsTypeHex]
	if !ok {
		return "UNKNOWN"
	}
	return fsTypeString
}

// GetInfo returns total and free bytes available in a directory, e.g. `/`.
func GetInfo(path string, _ bool) (info Info, err error) {
	s := syscall.Statfs_t{}

  // the tensor handle can be an error and return non-OK status.
  virtual absl::Status TensorHandleStatus() const;

  // Returns tensor shape. If tensor has unknown rank, shape remains untouched.
  virtual absl::Status Shape(tensorflow::PartialTensorShape* shape) const = 0;

  // Returns tensor (full) type.
  // While there is no immediate plan to deprecate dtype and shape in favor

from typing import Union

from fastapi import Depends, FastAPI
from fastapi.testclient import TestClient

app = FastAPI()


async def common_parameters(
    q: Union[str, None] = None, skip: int = 0, limit: int = 100
):
    return {"q": q, "skip": skip, "limit": limit}


@app.get("/items/")
async def read_items(commons: dict = Depends(common_parameters)):
    return {"message": "Hello Items!", "params": commons}

```Python hl_lines="7"
{!> ../../docs_src/query_params_str_validations/tutorial001_py310.py!}
```

////

🔢 🔢 `q` 🆎 `Union[str, None]` (⚖️ `str | None` 🐍 3️⃣.1️⃣0️⃣), 👈 ⛓ 👈 ⚫️ 🆎 `str` ✋️ 💪 `None`, & 👐, 🔢 💲 `None`, FastAPI 🔜 💭 ⚫️ 🚫 ✔.

/// note

FastAPI 🔜 💭 👈 💲 `q` 🚫 ✔ ↩️ 🔢 💲 `= None`.

 `Union` `Union[str, None]` 🔜 ✔ 👆 👨‍🎨 🤝 👆 👍 🐕‍🦺 & 🔍 ❌.

///

## 🌖 🔬

from typing import Set, Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None
    tags: Set[str] = set()


@app.post("/items/", response_model=Item, summary="Create an item")
async def create_item(item: Item):
    """
    Create an item with all the information:

    assert is_bytes_sequence_annotation(Union[List[str], List[bytes]])


def test_is_uploadfile_sequence_annotation():
    # For coverage
    # TODO: in theory this would allow declaring types that could be lists of UploadFile
    # and other types, but I'm not even sure it's a good idea to support it as a first
    # class "feature"
    assert is_uploadfile_sequence_annotation(Union[List[str], List[UploadFile]])

    </body>
</html>
"""


@app.get("/")
async def get():
    return HTMLResponse(html)


async def get_cookie_or_token(
    websocket: WebSocket,
    session: Annotated[Union[str, None], Cookie()] = None,
    token: Annotated[Union[str, None], Query()] = None,
):
    if session is None and token is None:
        raise WebSocketException(code=status.WS_1008_POLICY_VIOLATION)
    return session or token