private NodeBuilder<V> insertAndGetRoot(Entry<V> entry) {
        NodeBuilder<V> node = insertChild(null, entry.path, entry.value, entry.hasHighPrecedence);
        // Only the root node has no parent.
        for (;;) {
            final NodeBuilder<V> parent = node.parent;
            if (parent == null) {
                return node;
            }
            node = parent;
        }
    }
Inserts the first route and gets the root node of the trie.
core/src/main/java/com/linecorp/armeria/server/RoutingTrieBuilder.java