FastAPI StreamingResponse media_type="application/pdf"

I am trying to return a pdf file as

return StreamingResponse(generator, headers={"Content-Disposition": filename}, media_type="application/pdf")

Also, I raise an error if the file is not found

raise HTTPException(HTTP_404_NOT_FOUND, "File not found")

The problem is that redoc shows

RESPONSE SCHEMA: application/json

I need the response schema to be application/pdf when successful, and application/json when error occurs.

I tried using response_class and responses in the decorator @router.get(), but neither of them worked :(