[Python] item_state = attributes.instance_state(item)

here is my model.py
from sqlalchemy import create_engine, Column, Integer, String, ForeignKey, Table
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, relationship
from enum import Enum as PyEnum


SQLALCHEMY_DATABASE_URL = "sqlite:///./test.db"


engine = create_engine(SQLALCHEMY_DATABASE_URL, connect_args={"check_same_thread": False}) SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine) Base = declarative_base()

class Gender(PyEnum):
male = "male"
female = "female"

class Role(PyEnum):
admin = "admin"
student = "student"


user_roles = Table(
"user_roles",
Base.metadata,
Column("user_id", Integer, ForeignKey("users.id"), primary_key=True),
Column("role_id", Integer, ForeignKey("roles.id"), primary_key=True),)

class RoleTable(Base):
__tablename__ = "roles"
id = Column(Integer, primary_key=True, index=True)
name = Column(String, unique=True, nullable=False) # ✅ Store as a string instead of Enum

# Many-to-Many relationship with User
users = relationship("User", secondary=user_roles, back_populates="roles")

class User(Base):
__tablename__ = "users"
id = Column(Integer, primary_key=True, index=True)
first_name = Column(String, nullable=False)
middle_name = Column(String, nullable=True)
last_name = Column(String, nullable=False)
email = Column(String, unique=True, index=True, nullable=False)
password = Column(String, nullable=False)
gender = Column(String, nullable=False) # ✅ Store gender as a string
roles = relationship("RoleTable", secondary=user_roles, back_populates="users") # ✅ Fix relationship


Base.metadata.create_all(bind=engine)

I received this error and i do not know what to do since am still learning backend with fastapi: File "C:\Users\flex zone\venv\lib\site-packages\sqlalchemy\orm\unitofwork.py", line 63, in append
item_state = attributes.instance_state(item)


AttributeError: 'str' object has no attribute '_sa_instance_state'

here is my schema.py code from my project

from pydantic import BaseModel, EmailStr
from typing import List, Optional
from enum import Enum

class Gender(str, Enum):
male = "male"
female = "female"

class Role(str, Enum):
admin = "admin"
student = "student"



class UserBase(BaseModel):
first_name: str
middle_name: Optional[str] = None
last_name: str
email: EmailStr
password: str
gender: Gender
roles: List[str] # ✅ Expect List of role names (not RoleTable)


class Config:
orm_mode = True

class UserResponse(UserBase):
id: int


class UserCreate(UserBase):
pass


route.py

from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.orm import Session
from database import SessionLocal
from models.user_model import User, RoleTable
from schemas.user_schema import UserCreate, UserResponse
from typing import List


router = APIRouter()
def get_db():
db = SessionLocal()
try:
yield db
finally:
db.close()

router.post("/", response_model=UserResponse)
def create_user(user: UserCreate, db: Session = Depends(get_db)):
# Check if email already exists
existing_user = db.query(User).filter(User.email == user.email).first()
if existing_user:
raise HTTPException(status_code=400, detail="Email already registered")

# ✅ Convert role names (strings) into RoleTable instances
role_objects = db.query(RoleTable).filter(RoleTable.name.in_(user.roles)).all()

if len(role_objects) != len(user.roles): # Make sure all roles are valid
raise HTTPException(status_code=400, detail="One or more invalid roles provided")

# ✅ Create user object and assign roles (as RoleTable instances)
new_user = User(
first_name=user.first_name,
middle_name=user.middle_name,
last_name=user.last_name,
email=user.email,
password=user.password, # Hash this in real apps
gender=user.gender,
roles=role_objects # Store as RoleTable objects
)

# ✅ Save to database
db.add(new_user)
db.commit()
db.refresh(new_user)

# ✅ Convert RoleTable objects to strings for response
new_user_roles = [role.name for role in new_user.roles] # Just use role.name as it's already a string

# Manually update the roles before returning
new_user.roles = new_user_roles

return new_user


am working with PyCharm and am i a young developer still learning i received error when try to create a new post from the browser

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