code: func (kf *KeyFormat) Fix(args ...interface{}) (*KeyFormat, error) {
  	key, err := kf.Key(args...)
  	if err != nil {
  		return nil, err
  	}
  	return NewKeyFormat(string(key), kf.layout[len(args):]...)
  }
docs: // Fixes the first args many segments as the prefix of a new KeyFormat by using the args to generate a key that becomes
  // that prefix. Any remaining unassigned segments become the layout of the new KeyFormat.