old_contents: # -*- coding: utf-8 -*-
  
  from flask import Flask
  from flask_sqlalchemy import SQLAlchemy
  
  
  app = Flask(__name__)
  app.config.from_object('url_shortener.default_config')
  app.config.from_envvar('URL_SHORTENER_CONFIGURATION')
  db = SQLAlchemy(app)
  
new_contents: # -*- coding: utf-8 -*-
  
  from flask import Flask
  from flask_sqlalchemy import SQLAlchemy
  
  
  app = Flask(__name__)
  app.config.from_object('url_shortener.default_config')
  """
  From http://flask-sqlalchemy.pocoo.org/2.1/config/:
  
  "SQLALCHEMY_TRACK_MODIFICATIONS - If set to True, Flask-SQLAlchemy
  will track modifications of objects and emit signals. The default is
  None, which enables tracking but issues a warning that it will be
  disabled by default in the future. This requires extra memory and
  should be disabled if not needed."
  
  This application uses SQLAlchemy event system, so this value is set
  to False
  """
  app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
  app.config.from_envvar('URL_SHORTENER_CONFIGURATION')
  db = SQLAlchemy(app)
  
subject: Set SQLALCHEMY_TRACK_MODIFICATIONS option to False