Can't access model attributes from statement in SQLModel

Question

I'm using SQLModel on my project with FastAPI. All worked perfectly until my requests "lost" their attributes.

On another file with similar code, I can access attributes simply using subtask.order_nb as show in the SQLModel documentation.

But now, I can only access using subtask._data[0].order_nb which is not the best way to handle this. If I try to change attributes "order_nb" I get an error

    raise AttributeError("can't set attribute")
AttributeError: can't set attribute

Here the model for "Subtask"

class Subtask(SQLModel, table=True):
    subtask_id:int = Field(default=None, primary_key=True)
    subtask_key:str = Field(default=None, nullable=False)
    subtask_status:str = Field(sa_column=Column(Enum(SubtaskStatus)), nullable=False)
    order_nb:int = Field(default=None, nullable=False)
    gitlab_project_name:str = Field(default=None, nullable=False)
    gitlab_project_id:int = Field(default=None, nullable=False)
    fk_issue_id:int = Field(default=None, foreign_key="issue.issue_id", nullable=False)

Here my fastAPI code:

from fastapi import APIRouter, Depends
from sqlalchemy import select
from sqlmodel import func
from sqlmodel import Session
from interfaces.gitlab import GitlabResponse
from jira.service import change_subtask_status, change_issue_status
from jira.models import Subtask, Issue, IssueStatus
from db import get_session

router = APIRouter()
@router.post("/gitlab_callbacks")
async def get_gitlab_callbacks(request: GitlabResponse, session: Session = Depends(get_session)):
    print(request)
    statement = select(Subtask).where(Subtask.subtask_id == request.subtask_id)
    subtask = session.exec(statement).first()

db.py

import os

from sqlmodel import SQLModel, Session, create_engine

#import models # Imported models will be created with SQL Engine
from deployments import models
from jira import models
from jira.models import Issue, Subtask
from dotenv import load_dotenv

load_dotenv()

engine = create_engine(os.environ.get("DATABASE_URL"), echo=False, future=True)


def init_db():
    """Initialize SQL engine"""
    if os.environ.get('MODE') == 'DEV':
        SQLModel.metadata.drop_all(engine)
    SQLModel.metadata.create_all(engine)

def get_session() -> Session:
    """Get the SQL engine session"""
    with Session(engine) as session:
        return session

I don't know where I made a mistake.

Thanks for your help