How to make simple JSON DataDriver

I am having trouble making a very simple JSON DataDriver. I want to load direct json into a tree, using every key as the value. I have tried making a DataDriver but this is not working. Is there a simple way to use every value in the JSON as an entry in a tree?

Here is my not working example: https://snippet.webix.com/t5fkh09r

Hello,

Please, check the sample: Code Snippet
How to customize data driver you can find here.