code: def bind_extensions(app):
      
      # bind plugin to app object
      app.db = app.config['PUZZLE_BACKEND']
      app.db.init_app(app)
  
      # bind bootstrap blueprints
      bootstrap.init_app(app)
      markdown(app)
  
      @app.template_filter('islist')
      def islist(object):
          return isinstance(object, (tuple, list))
docs: Configure extensions.
  
      Args:
          app (Flask): initialized Flask app instance