code: def init_app(app):
      
      config = EmailsConfig(app)
      # register extension with app
      app.extensions = getattr(app, 'extensions', {})
      app.extensions['emails'] = config
      return config
docs: 'Initialize' flask application.
      It creates EmailsConfig object and saves it in app.extensions.
  
      You don't have to call this method directly.
  
      :param app: Flask application object
      :return: Just created :meth:`~EmailsConfig` object