How can a parameter name support multiple variable types？

[xxddccaa]

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Example Code

# -*- coding:utf-8 -*-
import traceback
from typing import Optional
import uvicorn
from fastapi import FastAPI, File, Form, UploadFile

app = FastAPI()


@app.post("/filesper/")
def filesper(
        file: Optional[UploadFile, bytes, str] = Optional[File(...), Form(...)],
):
    try:
        if file:
            return 1
    except:
        traceback.print_exc()
        return -1


if __name__ == '__main__':
    uvicorn.run('testfastapi:app', host='0.0.0.0', port=8001, reload=False, debug=False, workers=1)

Description

hello!
How can a parameter variable name support multiple types？
In the program，file: Optional[UploadFile, bytes, str] = Optional[File(...), Form(...)]，this program is my imagination，I want file parameter can be anything that I need, isinstance() can be used to distinguish detail types.
I don't think it can succeed, but I want to know why.
thank you!

Operating System

Linux

Operating System Details

CentOS 7

FastAPI Version

0.68.0

Python Version

Additional Context

[xxddccaa]

Python 3.8.11

[panla]

from typing import Union

variable = Union[str, int, dict, float]
variable = Optional[Union[str, int, dict, float]]

[xxddccaa]

from typing import Union

variable = Union[str, int, dict, float]
variable = Optional[Union[str, int, dict, float]]

thank you!
Python general types can indeed be written like your code, but url FORM information and FILE information do not seem to be able to do so. I want to express FORM and FILE .

This is a practical application scenario. When I want to pass in a picture or a URL to the url interface, it seems to the user that it is the same thing, so I want to express it with the same parameter.