```

O parâmetro de consulta `q` é do tipo `Union[str, None]`, o que significa que é do tipo `str` mas que também pode ser `None`, e de fato, o valor padrão é `None`, então o FastAPI saberá que não é obrigatório.

/// note | "Observação"

O FastAPI saberá que o valor de `q` não é obrigatório por causa do valor padrão `= None`.

from typing import List, 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: List[str] = []


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

from typing import Set, Union

from fastapi import FastAPI, status
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, status_code=status.HTTP_201_CREATED)
async def create_item(item: Item):

class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: list[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str

from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/items/{item_id}")
async def read_user_item(
    item_id: str, needy: str, skip: int = 0, limit: Union[int, None] = None
):
    item = {"item_id": item_id, "needy": needy, "skip": skip, "limit": limit}

from typing import Annotated, Union

from fastapi import Cookie, Depends, FastAPI

app = FastAPI()


def query_extractor(q: Union[str, None] = None):
    return q


def query_or_cookie_extractor(
    q: Annotated[str, Depends(query_extractor)],
    last_query: Annotated[Union[str, None], Cookie()] = None,
):
    if not q:
        return last_query
    return q


@app.get("/items/")
async def read_query(

from typing import Union

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Union[bytes, None] = File(default=None)):
    if not file:
        return {"message": "No file sent"}
    else:
        return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: Union[UploadFile, None] = None):
    if not file:

     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getDevelopmentHere();

    /**
     * Is the property for the key 'development.here' true? <br>
     * The value is, e.g. true <br>
     * comment: Is development environment here? (used for various purpose, you should set false if unknown)

        val dependency = when (val result = queue.removeFirst()) {
            is ResolvedDependencyResult -> result
            is UnresolvedDependencyResult -> throw result.failure
            else -> throw AssertionError("Unknown dependency type: $result")
        }

        if (dependency.isConstraint) {
            continue
        }

        val to = dependency.resolvedVariant

        when (val fromComponent = dependency.from.id) {

from typing import Union

from fastapi import FastAPI, Query
from typing_extensions import Annotated

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Annotated[Union[str, None], Query(title="Query string", min_length=3)] = None,
):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})