code: def post_create_app(cls, app, **settings):
          
          super(MarshmallowAwareApp, cls).post_create_app(app, **settings)
  
          marsh.init_app(app)
  
          return app
docs: Automatically register and init the Flask Marshmallow extension.
  
          Args:
              app (flask.Flask): The application instance in which to initialize
                  Flask Marshmallow upon.
  
          Kwargs:
              settings (dict): The settings passed to this method from the
                  parent app.
  
          Returns:
              flask.Flask: The Flask application that was passed in.