src/vs/base/common/map.ts/TernarySearchTree/_getNode
class TernarySearchTree:	private _getNode(key: K) {
		const iter = this._iter.reset(key);
		let node = this._root;
		while (node) {
			const val = iter.cmp(node.segment);
			if (val > 0) {
				// left
				node = node.left;
			} else if (val < 0) {
				// right
				node = node.right;
			} else if (iter.hasNext()) {
				// mid
				iter.next();
				node = node.mid;
			} else {
				break;
			}
		}
		return node;
	}