for method in route.methods:
            operation = get_openapi_operation_metadata(
                route=route, method=method, operation_ids=operation_ids
            )
            parameters: List[Dict[str, Any]] = []
            flat_dependant = get_flat_dependant(route.dependant, skip_repeats=True)
            security_definitions, operation_security = get_openapi_security_definitions(
                flat_dependant=flat_dependant

from fastapi import FastAPI
from fastapi.openapi.utils import get_openapi

app = FastAPI()


@app.get("/items/")
async def read_items():
    return [{"name": "Foo"}]


def custom_openapi():
    if app.openapi_schema:
        return app.openapi_schema
    openapi_schema = get_openapi(
        title="Custom title",
        version="2.5.0",
        summary="This is a very custom OpenAPI schema",

        "/a": {
            "get": {
                "responses": {
                    # this is how one would imagine the openapi schema to be
                    # but since the key is not valid, openapi.utils.get_openapi will raise ValueError
                    "hello": {"description": "Not a valid additional response"},
                    "200": {
                        "description": "Successful Response",

By default, what the method `.openapi()` does is check the property `.openapi_schema` to see if it has contents and return them.

If it doesn't, it generates them using the utility function at `fastapi.openapi.utils.get_openapi`.

And that function `get_openapi()` receives as parameters:

* `title`: The OpenAPI title, shown in the docs.
* `version`: The version of your API, e.g. `2.5.0`.

如果 `.openapi_schema` 属性没有内容，该方法就使用 `fastapi.openapi.utils.get_openapi` 工具函数生成内容。

`get_openapi()` 函数接收如下参数：

* `title`：文档中显示的 OpenAPI 标题
* `version`：API 的版本号，例如 `2.5.0`
* `openapi_version`： OpenAPI 规范的版本号，默认为最新版： `3.0.2`
* `description`：API 的描述说明
* `routes`：路由列表，每个路由都是注册的*路径操作*。这些路由是从 `app.routes` 中提取的。

## 覆盖默认值

`get_openapi()` 工具函数还可以用于生成 OpenAPI 概图，并利用上述信息参数覆盖指定的内容。

⚫️ 📨 🎻 📨 ⏮️ 🏁 🈸 `.openapi()` 👩‍🔬.

🔢, ⚫️❔ 👩‍🔬 `.openapi()` 🔨 ✅ 🏠 `.openapi_schema` 👀 🚥 ⚫️ ✔️ 🎚 & 📨 👫.

🚥 ⚫️ 🚫, ⚫️ 🏗 👫 ⚙️ 🚙 🔢 `fastapi.openapi.utils.get_openapi`.

& 👈 🔢 `get_openapi()` 📨 🔢:

* `title`: 🗄 📛, 🎦 🩺.
* `version`: ⏬ 👆 🛠️, ✅ `2.5.0`.
* `openapi_version`: ⏬ 🗄 🔧 ⚙️. 🔢, ⏪: `3.0.2`.
* `description`: 📛 👆 🛠️.

Ist das nicht der Fall, wird der Inhalt mithilfe der Hilfsfunktion unter `fastapi.openapi.utils.get_openapi` generiert.

Und diese Funktion `get_openapi()` erhält als Parameter:

* `title`: Der OpenAPI-Titel, der in der Dokumentation angezeigt wird.
* `version`: Die Version Ihrer API, z. B. `2.5.0`.

from fastapi.logger import logger
from fastapi.openapi.docs import (
    get_redoc_html,
    get_swagger_ui_html,
    get_swagger_ui_oauth2_redirect_html,
)
from fastapi.openapi.utils import get_openapi
from fastapi.params import Depends
from fastapi.types import DecoratedCallable, IncEx
from fastapi.utils import generate_unique_id
from starlette.applications import Starlette
from starlette.datastructures import State