[Python] Can't get correct server response on validation error (spectree + flask )

I have a problem with my API on Flask, using spectree. I have one endpoint with one "POST" method, which takes some data, validates it, and if successful, returns {"status": "OK"}, and in case of validation error, returns a 400 code and a message that there was a validation error. It is rather not what I have, but what I wanted to achieve. I suggest taking a look at the code to better understand what I mean:

from flask import Flask
from spectree import SpecTree, Response
from pydantic import BaseModel

class Error(BaseModel):
code:int = 400
message:str = 'Validation Failed'

class Unit(BaseModel):
id: int

app = Flask(__name__)
api = SpecTree('flask', app=app, title='API', version='v1.0', path='docs')

@app.post('/imports')
@api.validate(json=Unit, validation_error_status=400, resp=Response(HTTP_400=Error))
def imports():
return {'status': 'OK'}, 200


That is, as you can see, following the documentation, I set validation_error_status=400 so that when validation fails, the client receives a response with a 400 code (wow?). I also set resp=Response(HTTP_400=Error) so that when a 400 error occurs, the client receives an Error response. Thus, on a validation error, the API client should receive a response corresponding to the Error model (see below)

Now, if I send a request that is not valid, that is, id will not be int, but for example "fkfld", I will receive the following response:

[
{
"loc": [
"id"
],
"msg": "value is not a valid integer",
"type": "type_error.integer"
}
]


I thought the answer would be:

{
"code": 400,
"message": "Validation Failed"
}


I use:

• Python 3.8.3
• Flask 2.1.2
• spectree 0.10.0

I tried very hard to understand what my mistake was, but I could not. I've read the documentation, but my problem is only related to:

What is Response and how to use it?

To build a response for the endpoint, you need to declare the status code with format HTTP_{code} and corresponding data (optional).
​

Please help me figure this out, I really want to understand my mistakes and how to do it right.

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