code: func (e *Error) Stack() string {
  	if len(e.stacks) > 0 {
  		var frames []string
  		for _, stack := range e.stacks {
  			if frames == nil {
  				frames = make([]string, 0, len(stack))
  			} else {
  				frames = append(frames, "----- attached stack -----")
  			}
  			for _, f := range stack {
  				frames = append(frames, f.String())
  			}
  		}
  		return strings.Join(frames, "\n")
  	}
  	return ""
  }
docs: // Stack will return the stack associated with the error if one is found. You
  // probably want the package-level GetStack.