code: func (c *Change) Action() (Action, error) {
  	if c.From == nil && c.To == nil {
  		return Action(0), fmt.Errorf("malformed change: nil from and to")
  	}
  	if c.From == nil {
  		return Insert, nil
  	}
  	if c.To == nil {
  		return Delete, nil
  	}
  
  	return Modify, nil
  }
docs: // Action is convenience method that returns what Action c represents.