$WORKSPACE/build_info/Cargo.toml[package]
The tree starts as a single region covering the whole space. As points arrive, they get dropped into the region that contains them. When a region exceeds its capacity (the maximum number of points it can hold before splitting), the region divides into four children, and the existing points get redistributed.
，更多细节参见新收录的资料
frame = frame.forestChild;
这两种说法都有道理，但仔细想想，可能都漏掉了一个关键。