APIKeyCookie,
    APIKeyHeader,
    APIKeyQuery,
    HTTPAuthorizationCredentials,
    HTTPBasic,
    HTTPBasicCredentials,
    HTTPBearer,
    HTTPDigest,
    OAuth2,
    OAuth2AuthorizationCodeBearer,
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    OAuth2PasswordRequestFormStrict,
    OpenIdConnect,
    SecurityScopes,
)
```

## API Key Security Schemes

                    headers={"WWW-Authenticate": "Bearer"},
                )
            else:
                return None
        return param


class OAuth2AuthorizationCodeBearer(OAuth2):
    """
    OAuth2 flow for authentication using a bearer token obtained with an OAuth2 code
    flow. An instance of it would be used as a dependency.
    """

    def __init__(

* Add link to Chinese article in [External Links](https://fastapi.tiangolo.com/external-links/). PR [810](https://github.com/tiangolo/fastapi/pull/810) by [@wxq0309](https://github.com/wxq0309).
* Implement `OAuth2AuthorizationCodeBearer` class. PR [#797](https://github.com/tiangolo/fastapi/pull/797) by [@kuwv](https://github.com/kuwv).