code: func (i *Image) History(tagName string) ([]string, error) {
  	layerID, ok := i.tags[tagName]
  	if !ok {
  		return nil, fmt.Errorf("can't find tag '%s' for image '%s'", tagName, i.Name)
  	}
  
  	var history []string
  	err := i.parseResponse(fmt.Sprintf("v1/images/%s/ancestry", layerID), &history)
  	if err != nil {
  		return nil, err
  	}
  	return history, nil
  }
docs: // History returns an ordered list of layers that make up Docker. The order is reverse, it goes from
  // the latest layer to the base layer. Client can iterate these layers and download them using LayerReader.