sqlalchemy many to many field with extra fields not getting updated

Question

I have two table user and film. These table have many to many relationship with extra field role. I am trying to update role if user and film matched. But this giving me error

user_film_table = Table(
  "user_film_association",
  Base.metadata,
  Column("id", Integer, primary_key=True, index=True),
  Column("user_id", ForeignKey("users.id"), index=True),
  Column("film_id", ForeignKey("film.id"), index=True),
  Column('role', ENUM(UserRoleEnum))  # Role can be 'writer', 'producer', or 'director' 
)

def update_user_role(self, user_id, film_id, new_role):
        user = self.db.query(User).filter(User.id == user_id).first()
        if not user:
            return HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")

        film = self.db.query(Film).filter(Film.id == film_id).first()
        if not film:          
            return HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Film not found")

        if film not in user.film:
            return HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User is not associated with the specified film")

        user_film = self.db.query(user_film_table).filter(user_film_table.c.user_id == user_id, user_film_table.c.film_id == film_id).first()
        print(user_film[0])
        user_film[3].role = new_role.value   #facing error while updating the role
        self.db.add(user_film)
        self.db.commit()
        return {"message": f"User role in film updated to {new_role} successfully", 'status_code': status.HTTP_202_ACCEPTED}

Not able to update the role in many to many field getting error

raise exc.UnmappedInstanceError(instance) from err
sqlalchemy.orm.exc.UnmappedInstanceError: Class 'sqlalchemy.engine.row.Row' is not mapped