private _entries(node: TernarySearchTreeNode<K, V> | undefined): IterableIterator<[K, V]> {
this._dfsEntries(node, result);
return result[Symbol.iterator]();
}
private _dfsEntries(node: TernarySearchTreeNode<K, V> | undefined, bucket: [K, V][]) {
if (!node) {
return;
}