UnityEditor.TreeViewDataSource.SetExpandedWithChildren C# (CSharp) Method

        public virtual void SetExpandedWithChildren(TreeViewItem fromItem, bool expand)
        {
            Stack<TreeViewItem> stack = new Stack<TreeViewItem>();
            stack.Push(fromItem);
            HashSet<int> other = new HashSet<int>();
            while (stack.Count > 0)
            {
                TreeViewItem item = stack.Pop();
                if (item.hasChildren)
                {
                    other.Add(item.id);
                    foreach (TreeViewItem item2 in item.children)
                    {
                        stack.Push(item2);
                    }
                }
            }
            HashSet<int> source = new HashSet<int>(this.expandedIDs);
            if (expand)
            {
                source.UnionWith(other);
            }
            else
            {
                source.ExceptWith(other);
            }
            this.SetExpandedIDs(source.ToArray<int>());
        }