code: func (state *DockerTaskEngineState) AddImageState(imageState *image.ImageState) {
  	if imageState == nil {
  		log.Debug("Cannot add empty image state")
  		return
  	}
  	if imageState.Image.ImageID == "" {
  		log.Debug("Cannot add image state with empty image id")
  		return
  	}
  	state.lock.Lock()
  	defer state.lock.Unlock()
  
  	state.imageStates[imageState.Image.ImageID] = imageState
  }
docs: // AddImageState adds an image.ImageState to be stored