a Tree Data Structure: a `Node` with Child Nodes
-->
<h4 id="木データ構造を作る-子ノードのあるnode"><a class="header" href="#木データ構造を作る-子ノードのあるnode">木データ構造を作る: 子ノードのある<code>Node</code></a></h4>
<!--
To start, we’ll build a tree with nodes that know about their child nodes.
We’ll create a struct named `Node` that holds its own `i32` value as well as
references to its children `Node` values:
-->
<p>手始めに子ノードを�