{!../../docs_src/python_types/tutorial009.py!}
```

Использование `Optional[str]` вместо просто `str` позволит редактору помочь вам в обнаружении ошибок, в которых вы могли бы предположить, что значение всегда является `str`, хотя на самом деле это может быть и `None`.

#### Generic-типы

Эти типы принимают параметры в квадратных скобках:

* `List`
* `Tuple`
* `Set`
* `Dict`
* `Optional`
* ...и др.

        final Date date = toDate(str, locale);
        if (date != null) {
            return new java.sql.Date(date.getTime());
        }
        final java.sql.Date sqlDate = toSqlDateJdbcEscape(str);
        if (sqlDate != null) {
            return sqlDate;
        }
        throw new ParseRuntimeException(str);
    }

    /**
     * 文字列を{@link Date}に変換します。
     *
     * @param str
     *            文字列

# Sponsors


class SponsorEntity(BaseModel):
    login: str
    avatarUrl: str
    url: str


class Tier(BaseModel):
    name: str
    monthlyPriceInDollars: float


class SponsorshipAsMaintainerNode(BaseModel):
    sponsorEntity: SponsorEntity
    tier: Tier


class SponsorshipAsMaintainerEdge(BaseModel):
    cursor: str
    node: SponsorshipAsMaintainerNode

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: List[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header()):

app = FastAPI()


def query_extractor(q: str | None = None):
    return q


def query_or_cookie_extractor(
    q: str = Depends(query_extractor), last_query: str | None = Cookie(default=None)
):
    if not q:
        return last_query
    return q


@app.get("/items/")
async def read_query(query_or_default: str = Depends(query_or_cookie_extractor)):

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: Annotated[CommonHeaders, Header()]):

from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    model_config = {"extra": "forbid"}

    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: List[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header()):

from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    class Config:
        extra = "forbid"

    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: List[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header()):

from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    class Config:
        extra = "forbid"

    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header()):

app = FastAPI()


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


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


@app.get("/items/")
async def read_query(query_or_default: str = Depends(query_or_cookie_extractor)):