QuerySet' object has no attribute 'username' code example

Example: AttributeError: type object 'User' has no attribute 'query'

import os
import sys
from sqlalchemy import Column, ForeignKey, Integer, String, DateTime, Boolean, Float, Date, Table
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship
from sqlalchemy import create_engine
from flask_security import Security, SQLAlchemyUserDatastore, UserMixin, RoleMixin, login_required

Base = declarative_base()

roles_users = Table('roles_users', Base.metadata, Column('user_id', Integer, ForeignKey('user.id')), Column('role_id', Integer, ForeignKey('role.id')))

class Role(Base, RoleMixin):
    __tablename__ = 'role'
    id = Column(Integer, primary_key=True)
    name = Column(String(80), unique=True)
    description = Column(String(255))

class User(Base, UserMixin):
    __tablename__ = 'user'

    id = Column(Integer, primary_key=True)
    email = Column(String(250), nullable=False)
    password = Column(String(30))
    last_login_at = Column(DateTime)
    active = Column(Boolean)
    confirmed_at = Column(DateTime)
    current_login_at = Column(DateTime)
    last_login_ip = Column(String(45))
    current_login_ip = Column(String(45))
    login_count = Column(Integer)