code: def init_extension(self, app):
          
          app.config.setdefault('CACHE_VERSION', '0')
          app.config.setdefault('CACHE_PREFIX', 'r')
          app.config.setdefault('CACHE_BACKEND', 'rio.exts.flask_cache.NullBackend')
          app.config.setdefault('CACHE_BACKEND_OPTIONS', {})
docs: Initialize cache instance.