在Dart中，如何复制/克隆2D列表？

List<List<T>> clone2DList<T>(List<List<T>> originalList) {
  List<List<T>> clonedList = [];
  for (int i = 0; i < originalList.length; i++) {
    List<T> row = [];
    for (int j = 0; j < originalList[i].length; j++) {
      row.add(originalList[i][j]);
    }
    clonedList.add(row);
  }
  return clonedList;
}

List<List<int>> originalList = [[1, 2], [3, 4]];
List<List<int>> clonedList = clone2DList(originalList);
print(clonedList); // [[1, 2], [3, 4]]

List<List<T>> clone2DList<T>(List<List<T>> originalList) {
  return originalList.map((row) => List<T>.from(row)).toList();
}

List<List<int>> originalList = [[1, 2], [3, 4]];
List<List<int>> clonedList = clone2DList(originalList);
print(clonedList); // [[1, 2], [3, 4]]