code: func (w *Wallet) URL() accounts.URL {
  	return accounts.URL{
  		Scheme: w.Hub.scheme,
  		Path:   fmt.Sprintf("%x", w.PublicKey[1:5]), // Byte #0 isn't unique; 1:5 covers << 64K cards, bump to 1:9 for << 4M
  	}
  }
docs: // URL retrieves the canonical path under which this wallet is reachable. It is
  // user by upper layers to define a sorting order over all wallets from multiple
  // backends.