How to mock pydantic BaseModel that expects a Response object?

I'm writing tests for my API client. I need to mock the get function so that it won't make any requests. So instead of returning a Response object I want to return a MagicMock. But then pydantic raises ValidationError because it is going to the model.

I have the following pydantic model:

class Meta(BaseModel):    raw: Optional[str]    response: Optional[Response]    class Config:        arbitrary_types_allowed = True

which raises:

>   ???E   pydantic.error_wrappers.ValidationError: 1 validation error for OneCallResponseE   meta -> responseE     instance of Response expected (type=type_error.arbitrary_type; expected_arbitrary_type=Response)

The one solution would be to add Union with MagicMock but I really don't want to change the code for tests. That is not the way.

class Meta(BaseModel):    raw: Optional[str]    response: Optional[Union[Response, MagicMock]]    class Config:        arbitrary_types_allowed = True

Any ideas how to patch/mock it?