text: from werkzeug.security import generate_password_hash, check_password_hash
  from itsdangerous import TimedJSONWebSignatureSerializer as Serializer
  from flask import current_app
  from flask_login import UserMixin
  from . import db, login_manager
  
  
  class Role(db.Model):
      __tablename__ = 'roles'
      id = db.Column(db.Integer, primary_key=True)
      name = db.Column(db.String(64), unique=True)
      users = db.relationship('User', backref='role', lazy='dynamic')
  
      def __repr__(self):
          return '<Role %r>' % self.name
  
  
  class User(UserMixin, db.Model):
      __tablename__ = 'users'
      id = db.Column(db.Integer, primary_key=True)
      email = db.Column(db.String(64), unique=True, index=True)
      username = db.Column(db.String(64), unique=True, index=True)
      role_id = db.Column(db.Integer, db.ForeignKey('roles.id'))
      password_hash = db.Column(db.String(128))
      confirmed = db.Column(db.Boolean, default=False)
  
      @property
      def password(self):
          raise AttributeError('password is not a readable attribute')
  
      @password.setter
      def password(self, password):
          self.password_hash = generate_password_hash(password)
  
      def verify_password(self, password):
          return check_password_hash(self.password_hash, password)
  
      def generate_confirmation_token(self, expiration=3600):
          s = Serializer(current_app.config['SECRET_KEY'], expiration)
          return s.dumps({'confirm': self.id}).decode('utf-8')
  
      def confirm(self, token):
          s = Serializer(current_app.config['SECRET_KEY'])
          try:
              data = s.loads(token.encode('utf-8'))
          except:
              return False
          if data.get('confirm') != self.id:
              return False
          self.confirmed = True
          db.session.add(self)
          return True
  
      def generate_reset_token(self, expiration=3600):
          s = Serializer(current_app.config['SECRET_KEY'], expiration)
          return s.dumps({'reset': self.id}).decode('utf-8')
  
      @staticmethod
      def reset_password(token, new_password):
          s = Serializer(current_app.config['SECRET_KEY'])
          try:
              data = s.loads(token.encode('utf-8'))
          except:
              return False
          user = User.query.get(data.get('reset'))
          if user is None:
              return False
          user.password = new_password
          db.session.add(user)
          return True
  
      def generate_email_change_token(self, new_email, expiration=3600):
          s = Serializer(current_app.config['SECRET_KEY'], expiration)
          return s.dumps(
              {'change_email': self.id, 'new_email': new_email}).decode('utf-8')
  
      def change_email(self, token):
          s = Serializer(current_app.config['SECRET_KEY'])
          try:
              data = s.loads(token.encode('utf-8'))
          except:
              return False
          if data.get('change_email') != self.id:
              return False
          new_email = data.get('new_email')
          if new_email is None:
              return False
          if self.query.filter_by(email=new_email).first() is not None:
              return False
          self.email = new_email
          db.session.add(self)
          return True
  
      def __repr__(self):
          return '<User %r>' % self.username
  
  
  class Assets(db.Model):
      __tablename__ = 'assets'
      id = db.Column(db.String(64), primary_key=True)
      description = db.Column(db.String(64), unique=True)
  
  class Portfolios(db.Model):
      __tablename__ = 'portfolios'
      id = db.Column(db.String(64), primary_key=True)
      description = db.Column(db.String(64), unique=True)
  
  class Weights(db.Model):
      __tablename__ = 'weights'
      port_id = db.Column(db.String(64), primary_key=True)
      port_date = db.Column(db.Date, unique=True)
      asset = db.Column(db.String(64), unique=False)
      weight = db.Column(db.Float, unique=False)
  
  @login_manager.user_loader
  def load_user(user_id):
      return User.query.get(int(user_id))
  