code: def _openapi_redoc(self):
          
          return render_template('openapi/redoc.html',
                                 title=self.app.config.API_TITLE or self.app.name,
                                 redoc_url=self.app.config.API_REDOC_SOURCE_URL)
docs: Expose OpenAPI spec with ReDoc
  
          The ReDoc script URL can be specified as ``API_REDOC_SOURCE_URL``