code: func (ks *KeyStore) ImportPreSaleKey(keyJSON []byte, passphrase string) (accounts.Account, error) {
  	a, _, err := importPreSaleKey(ks.storage, keyJSON, passphrase)
  	if err != nil {
  		return a, err
  	}
  	ks.cache.add(a)
  	ks.refreshWallets()
  	return a, nil
  }
docs: // ImportPreSaleKey decrypts the given Ethereum presale wallet and stores
  // a key file in the key directory. The key file is encrypted with the same passphrase.