code: func (container *Container) CheckpointTo(store ViewDB) error {
  	deepCopy, err := container.toDisk()
  	if err != nil {
  		return err
  	}
  	return store.Save(deepCopy)
  }
docs: // CheckpointTo makes the Container's current state visible to queries, and persists state.
  // Callers must hold a Container lock.