old_contents: import datetime, re;
  from sqlalchemy.orm import validates;
  from server import DB, FlaskServer;
  
  
  class User_roles(DB.Model):
  	id = DB.Column(DB.Integer, primary_key=True, autoincrement=True);
  	user_id = DB.Column(DB.Integer, DB.ForeignKey('user.id'));
  	role_id = DB.Column(DB.Integer, DB.ForeignKey('roles.id'));
  	created_by = DB.Column(DB.Integer, DB.ForeignKey('users.id'));
  	created_at = DB.Column(DB.DateTime);
  	updated_by = DB.Column(DB.Integer, DB.ForeignKey('users.id'), nullable=True);
  	updated_at = DB.Column(DB.DateTime, nullable=True);
  		
  
new_contents: import datetime, re;
  from sqlalchemy.orm import validates;
  from server import DB, FlaskServer;
  
  
  class User_roles(DB.Model):
  	id = DB.Column(DB.Integer, primary_key=True, autoincrement=True);
  	user_id = DB.Column(DB.Integer, DB.ForeignKey('user.id'));
  	role_id = DB.Column(DB.Integer, DB.ForeignKey('roles.id'));
  	created_by = DB.Column(DB.Integer, DB.ForeignKey('users.id'));
  	created_at = DB.Column(DB.DateTime);
  	updated_by = DB.Column(DB.Integer, DB.ForeignKey('users.id'));
  	updated_at = DB.Column(DB.DateTime, nullable=True);
  		
  
subject: Update users_roles.py