question: private static String addInvalidKey ( List < Optional < AccountSshKey > > keys , String pub ) { AccountSshKey . Id keyId = new AccountSshKey . Id ( new Account . Id ( 1 ) , keys . size ( ) + 1 ) ; AccountSshKey key = new AccountSshKey ( keyId , pub ) ; key . setInvalid ( ) ; keys . add ( Optional . of ( key ) ) ; return AuthorizedKeys . INVALID_KEY_COMMENT_PREFIX + key . getSshPublicKey ( ) + "\n" ; }
target:  Adds the given public key as invalid SSH key to the given list.