old_contents: from flask import Flask
  
  app = Flask(__name__)
  
  @app.route('/')
  def hello():
      return "Hello World!"
  
  if __name__ == '__main__':
      app.run()
new_contents: import os 
  
  from flask import Flask
  from flask.ext.sqlalchemy import SQLAlchemy
  
  app = Flask(__name__)
  
  app.config['SQLALCHEMY_DATABASE_URI'] = os.environ.get("DATABASE_URI")
  track_modifications = app.config.setdefault(
      'SQLALCHEMY_TRACK_MODIFICATIONS',
      True,
  )
  db = SQLAlchemy(app)
  
  @app.route('/')
  def hello():
      return "Hello World!"
  
  if __name__ == '__main__':
      app.run()
subject: ADD DB configuration