public @Nullable TreeNode tryInsert(String s) {
        Map<String, TreeNode> childMap = getChildMap();
        if (!allowInsert(this)) {
            return null;
        }
        return childMap.computeIfAbsent(s, x -> new TreeNode(this));
    }
Represents one "branch" or "level" of the node tree
common/src/main/java/me/lucko/luckperms/common/treeview/TreeNode.java