delete method
Implementation
@override
Future<void> delete(key, reason) async {
_isInitialized();
if (!map.containsKey(key)) return;
logger.d('Deleting value');
logger.v({
'type': "method",
'method': "delete",
'key': key,
'reason': reason.toJson(),
});
map.remove(key);
await _persist();
}