A recursive `<TreeNode>` component renders its children by mapping over `node.children` and rendering `<TreeNode>` for each. You forget to add a `key`. Beyond the console warning, what concrete bug is most likely when a node is inserted in the middle of a sibling list?
function TreeNode({ node }) {
return (
<li>
{node.label}
<ul>
{node.children.map((c) => (
<TreeNode node={c} />
))}
</ul>
</li>
);
}