Write constructor
Implementation
Write({this.putItem, this.deleteKey}) {
if (!(putItem == null || deleteKey == null)) {
throw ArgumentError('Either putItem or deleteKey has to be null,'
" both can't be set in the same Write object");
}
if (putItem == null && deleteKey == null) {
throw ArgumentError('Either putItem or deleteKey has to be non null');
}
}