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: Annotated[CommonHeaders, Header()]):

import okhttp3.internal.commonCacheResponse
import okhttp3.internal.commonClose
import okhttp3.internal.commonCode
import okhttp3.internal.commonEmptyResponse
import okhttp3.internal.commonHeader
import okhttp3.internal.commonHeaders
import okhttp3.internal.commonIsRedirect
import okhttp3.internal.commonIsSuccessful
import okhttp3.internal.commonMessage
import okhttp3.internal.commonNetworkResponse

from pydantic import BaseModel

app = FastAPI()


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


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