```

Read the new docs: [Query Parameter Models](https://fastapi.tiangolo.com/tutorial/query-param-models/).

#### `Header` Parameter Models

Use Pydantic models for `Header` parameters:

```python
from typing import Annotated

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    host: str

import pytest
from fastapi import FastAPI, Header
from fastapi.testclient import TestClient
from pydantic import BaseModel, Field

app = FastAPI()

# =====================================================================================
# Without aliases


@app.get("/optional-list-str")
async def read_optional_list_str(
    p: Annotated[Optional[list[str]], Header()] = None,
):
    return {"p": p}

class ParameterInType(Enum):
    query = "query"
    header = "header"
    path = "path"
    cookie = "cookie"


class Encoding(BaseModelWithConfig):
    contentType: Optional[str] = None
    headers: Optional[dict[str, Union["Header", Reference]]] = None
    style: Optional[str] = None
    explode: Optional[bool] = None