code: func (x *XC) EmailFromKey(ctx context.Context, id string) string {
  	if key := x.pubring.Get(id); key != nil {
  		return key.Identity.Email
  	}
  	if key := x.secring.Get(id); key != nil {
  		return key.PublicKey.Identity.Email
  	}
  	return id
  }
docs: // EmailFromKey extracts the email from a key