addValue method
Add a key/value pair to the node.
Adds a K/V tuple to the node. The key must not exist prior adding.
Implementation
@override
Future<void> addValue(NodeValue value) async {
await _init();
if (await _getValue(value.key) != null) {
throw StorageException(
'value "${value.key}" does already exist in the node "$path"');
}
lastModified = DateTime.now().millisecondsSinceEpoch;
value.lastModified = lastModified;
_values[value.key] = value;
}