DTree_Node:MakeFolder ?

Hi everyone,
I wanted to make a DTree to show all folders, subfolders and files in a folder in garrysmod/data but the function MakeFolder doesn’t work for me.
So I found it in garrysmod\lua\vgui but when I tried to use it, no error, but nothing in my DTree

Here is my code for the tree, tell me if you see a problem

	local DataList = vgui.Create("DTree", Frame)
	local Root = DataList:AddNode("Generator", "icon16/computer.png")
	Root:MakeFolder("data", "mydata/", true, "*.txt" )

Here is the code of the function if you want to see it https://github.com/Facepunch/garrysmod/blob/master/garrysmod/lua/vgui/dtree_node.lua