code: func DecodeKeys(a ...string) ([]*Key, error) {
  	if len(a) == 0 {
  		return nil, errNoKeys
  	}
  	var err error
  	ks := make([]*Key, len(a))
  	for i, s := range a {
  		ks[i], err = DecodeKey(s)
  		if err != nil {
  			return nil, err
  		}
  	}
  	return ks, nil
  }
docs: // DecodeKeys decodes each element of a using DecodeKey and returns the
  // resulting keys. Requires at least one key.