new_contents: from app import db
  
  class Car(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      brand = db.Column(db.String(100))
      model = db.Column(db.String(100))
      price = db.Column(db.Float)
      available = db.Column(db.Boolean, default=True)
      picture_url = db.Column(db.String(250))
      ratings = db.relationship('Ratings', backref='car', lazy='dynamic')
  
      def __init__(self, brand, model, price, picture_url='static/img/default.jpg', available=True):
          self.brand = brand
          self.model = model
          self.price = price
          self.available = available
          self.picture_url = picture_url
  
      def __repr__(self):
          return '<Car %s - %s>' % (self.brand, self.model)
  
  class Rating(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      name = db.Column(db.String(100))
      rating = db.Column(db.Integer)
      car_id = db.Column(db.Integer, db.ForeignKey('car.id'))
  
      def __init__(self, name, car, rating):
          self.name = name
          self.car_id = car
  
      def __repr__(self):
          return '<Rating %s: %d>' % (self.name, self.rating)
  
subject: Add base models for car and rating