code: func (f *OutputFormat) Set(s string) error {
  	for _, of := range []OutputFormat{fmtJSON, fmtYAML} {
  		if s == string(of) {
  			*f = of
  			return nil
  		}
  	}
  	return fmt.Errorf("unknown output format %q", s)
  }
docs: // Set validates and sets the value of the OutputFormat