code: func (e *FieldEntry) String() string {
  	value := e.Value
  	if s, ok := value.(fmt.Stringer); ok {
  		value = s.String()
  	}
  
  	switch v := value.(type) {
  	case string:
  		return fmt.Sprintf("%q:%q", e.Key, v)
  
  	case error:
  		return fmt.Sprintf("%q:%q", e.Key, v.Error())
  
  	default:
  		return fmt.Sprintf("%q:%#v", e.Key, v)
  	}
  }
docs: // String returns the string representation of the field entry:
  // "<key>":"<value>".