Onclick of Button Expand KendoUI TreeView in Jquery

Dear All,

I am new to Kendo control, please help me with this, I already have Tree View as shown in the attachment, Now I have to Expand onclick of button, I know the code to perform Expand, but it doesn't expand complete child nodes, instead it does just only 1 immediate child, if it has more child, we need to keep clicking the Expand button then it does the expand. Please help me how to achive on single click to Expand all the Parent and Child nodes.

Its not repatitive question, I have already searched here,Please help me. Here expand is the button ID

This is My code:

$("#expand").on("click", function(){

var treeview = $("#treeview").data("kendoTreeView");

treeview.expand(".k-item");

})