Can dojo LazyTreeGrid be expanded all by default?

I want to expand LazyTreeGrid by default,but I find The defaultOpen option doesn't work, can we do some customization to expand the LazyTreeGrid? If we can please tell me how to do,thanks.

code Click here!Dojo LazyGreeGrid

Note:we can not use TreeGrid instead of LazyTreeGrid,because the checbox(s) in children items will not work well.