merge method
Implementation
void merge(FilterOptionGroup other) {
for (final AssetType type in _map.keys) {
_map[type] = _map[type]!.merge(other.getOption(type));
}
this.containsEmptyAlbum = other.containsEmptyAlbum;
this.containsPathModified = other.containsPathModified;
this.createTimeCond = other.createTimeCond;
this.updateTimeCond = other.updateTimeCond;
this.orders
..clear()
..addAll(other.orders);
}