code: def _reset(self):
          
          self.bundles = AttrDict()
          self._bundles = _DeferredBundleFunctionsStore()
          self.babel_bundle = None
          self.env = None
          self.extensions = AttrDict()
          self.services = AttrDict()
  
          self._deferred_functions = []
          self._initialized = False
          self._models_initialized = False
          self._services_initialized = False
          self._services_registry = {}
          self._shell_ctx = {}
docs: This method is for use by tests only!