code: func (re *Regexp) UnmarshalYAML(unmarshal func(interface{}) error) error {
  	var s string
  	if err := unmarshal(&s); err != nil {
  		return err
  	}
  	r, err := NewRegexp(s)
  	if err != nil {
  		return err
  	}
  	*re = r
  	return nil
  }
docs: // UnmarshalYAML implements the yaml.Unmarshaler interface.