findKey method
Find one key.
Returns null if not found.
Implementation
Future<K?> findKey(DatabaseClient databaseClient, {Finder? finder}) async {
final client = getClient(databaseClient);
var key = await client
.getSembastStore(this)
.txnFindKey(client.sembastTransaction, finder as SembastFinder?);
return (key as K?);
}