code: func (c *Cluster) ImageHistory(repo string) ([]docker.ImageHistory, error) {
  	img, err := c.storage().RetrieveImage(repo)
  	if err != nil {
  		return nil, err
  	}
  	node, err := c.getNodeByAddr(img.LastNode)
  	if err != nil {
  		return nil, err
  	}
  	imgHistory, err := node.ImageHistory(repo)
  	return imgHistory, wrapError(node, err)
  }
docs: // ImageHistory returns the history of a given image