class UsersChat(Base):
    __tablename__ = 'users_chat '
    __table_args__ = {'extend_existing': True}
 
    chat_id     = Column(Integer, ForeignKey('chats.id'), primary_key=True)
    user_id     = Column(Integer, ForeignKey('users.id'), unique=True, nullable=False)
    last_update = Column(Integer, onupdate=datetime.datetime.utcnow, default=datetime.datetime.now)
    cuStatus    = Column(ChoiceType(APP_USERSCHAT_TYPE), nullable=False)
 
 
class Chats(Base):
    __tablename__ = 'chats'
    __table_args__ = {'extend_existing': True}
    id = Column(Integer, primary_key=True)
    description = Column(Integer, nullable=False)
    users_chat = relationship('UsersChat', backref='chat', cascade='all, delete')
 
 
class Users(Base):
    __tablename__ = 'users'
    id            = Column(Integer, primary_key=True)
    firstname     = Column(String(128), nullable=False)
    lastname      = Column(String(128), nullable=False)
    password      = Column(String(128), nullable=False)
    users_chat    = relationship('UsersChat', backref='user', cascade='all, delete')

type(Users.users_chat)

ChoiceType(APP_USERSCHAT_TYPE)