Loading treeGrid in Snippet - Font Awesome not working

I am trying to load json data into a treegrid component.
However, it seems like the method setColTypes does not accept the value “tree”?

I am trying to make a snippet to demonstrate problems with Font Awesome.
Can you please help me make the snippet load tree grid data?

snippet.dhtmlx.com/ac9a8d508

Kind regards
Kermit

Unfortunately it is not available to crate a treegrid component on the snippets.dhtmlx.com as treegrid is available in PRO version of the dhtmlxSuite, while the sources of the STD version are used in the snippets.