old_contents: from flask_login import UserMixin
  from api.database import db
  
  class User(UserMixin, db.Model):
      __tablename__ = 'users'
      id = db.Column(db.Integer, primary_key=True)
      username = db.Column(db.String(80), unique=True)
      email = db.Column(db.String(80), unique=True)
      password = db.Column(db.String(80), unique=True)
new_contents: from flask_login import UserMixin
  from api.database import db
  
  class User(UserMixin, db.Model):
      __tablename__ = 'users'
      id = db.Column(db.Integer, primary_key=True)
      username = db.Column(db.String(80), unique=True)
      email = db.Column(db.String(80), unique=True)
      password = db.Column(db.String(80), unique=True)
      
      def __init__(self, username, email, password):
  		self.username = username
  		self.email = email
  		self.password = password
subject: add constructor for User