如何在typescript中输入具有动态字段名的树

interface Tree {
  [key: string]: Tree | string;
}

const tree: Tree = {
  root: {
    child1: "leaf1",
    child2: {
      grandchild1: "leaf2",
      grandchild2: "leaf3"
    }
  }
};

console.log(tree.root.child1); // 输出: leaf1
console.log(tree.root.child2.grandchild1); // 输出: leaf2