不正确的测试用例， 其中有个测试用例：输入nums:[2],val:3,期望输出[2],实际上我的代码输出的nums就是 [2]，但运行的结果还是现实我的结果是[],导致测试用例 一直过不了。

Given the root of a binary tree, each node in the tree has a distinct value. After deleting all nodes with a value in to_delete, we are left with a forest (a disjoint union of trees). Return the roots ...