code: func (r *FilesOrContents) String() string {
  	sliceOfString := make([]string, len([]FileOrContent(*r)))
  	for key, value := range *r {
  		sliceOfString[key] = value.String()
  	}
  	return strings.Join(sliceOfString, ",")
  }
docs: // String is the method to format the flag's value, part of the flag.Value interface.
  // The String method's output will be used in diagnostics.