(unity) find child recursively

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
 
public static class GameUtils
{
    //HOW TO USE
    //var cube = this.transform.FirstChildOrDefault(x => x.name == "deeply_nested_cube");
    public static Transform FirstChildOrDefault(this Transform parent, Func<Transform, bool> query)
    {
        if (parent.childCount == 0)
        {
            return null;
        }
 
        Transform result = null;
        for (int i = 0; i < parent.childCount; i++)
        {
            var child = parent.GetChild(i);
            if (query(child))
            {
                return child;
            }
            result = FirstChildOrDefault(child, query);
        }
 
        return result;
    }
 
 
    public static Transform SearchHierarchyForBone(Transform current, string name)
    {
        //sb.Append(current.name + "\n");
 
        // check if the current bone is the bone we're looking for, if so return it
        if (current.name == name)
            return current;
 
        // search through child bones for the bone we're looking for
        for (int i = 0; i < current.childCount; ++i)
        {
            // the recursive step; repeat the search one step deeper in the hierarchy
            var child = current.GetChild(i);
 
            Transform found = SearchHierarchyForBone(child, name);
 
            // a transform was returned by the search above that is not null,
            // it must be the bone we're looking for
            if (found != null)
                return found;
        }
 
        // bone with name was not found
        return null;
    }
}