text: import os
  
  from flask import Flask
  from flaskr import db, auth
  
  
  def create_app(test_config=None):
      app = Flask(__name__, instance_relative_config=True)
      app.config.from_mapping(
          SECRET_KEY='dev',
          DATABASE=os.path.join(app.instance_path, 'flaskr.sqlite'),
      )
  
      if test_config is None:
          app.config.from_pyfile('config.py', silent=True)
      else:
          app.config.from_mapping(test_config)
  
      try:
          os.makedirs(app.instance_path)
      except OSError:
          pass
  
      @app.route('/hello')
      def hello():
          return 'Hello, World!'
  
      db.init_app(app)
      app.register_blueprint(auth.bp)
      return app
  