Cannot drag Tree children with Drag-n-Drop extension about dgrid HOT 4 CLOSED

/**
 * Overriding function in Container.js to handle detecting Tree child nodes for DND
 */
_getChildByEvent: function(event) {
    var node = event.target;
    if (node) {
        for (var parent = node.parentNode; parent; node = parent, parent = node.parentNode) {
            // Check if the node is a dnd item and also a valid dgrid row (uppermost node under a containing div)
            if ((parent == this.parent || dojo.hasClass(parent, 'dgrid-tree-container'))
              && dojo.hasClass(node, 'dojoDndItem')) {
                return node;
            }
        }
    }
    return null;
}

        require(["dojo/_base/declare", "dojo/ready", "dojo/dom", "dojo/on", "dojo/_base/window", "dojo/_base/Deferred","dgrid/OnDemandGrid","dgrid/tree", "dgrid/Selection", "dgrid/Keyboard",  "dgrid/extensions/DnD", "dojo/store/Memory", "dojo/store/Observable", "dojo/store/util/QueryResults", "dojo/dnd/Source"],
                function(declare, ready, dojoDom, on, win, Deferred, OnDemandGrid, tree, Selection, Keyboard, DnD, Memory, Observable, QueryResults, DnDSource) {
                    ready(function() {

```
                    var testCountryStore = Observable(new Memory({
                        data: [
                            { id: 'US', name:'USA', type:'country', parent: 'NA' },
                            { id: 'New York', name:'New York', type:'city', parent: 'US' },
                            { id: 'Chicago', name:'Chicago', type:'city', parent: 'US' },
                            { id: 'Dallas', name:'Dallas', type:'city', parent: 'US' },
                            { id: 'Los Angeles', name:'Los Angeles', type:'city', parent: 'US' },
                            { id: 'Denver', name:'Denver', type:'city', parent: 'US' },
                            { id: 'Miami', name:'Miami', type:'city', parent: 'US' },
                            { id: 'Boston', name:'Boston', type:'city', parent: 'US' }
                        ],
                        getChildren: function(parent, options){
                            return this.query({parent: parent.id}, options);
                        },
                        mayHaveChildren: function(parent){
                            return parent.type != "city";
                        },
                        query: function(query, options){
                            var def = new Deferred();
                            var immediateResults = this.queryEngine(query, options)(this.data);
                            setTimeout(function(){
                                def.resolve(immediateResults);
                            }, 200);
                            var results = QueryResults(def.promise);
                            return results;
                        }
                    }));

                    var DnDGrid = declare([OnDemandGrid, Selection, DnD, Keyboard]);

                    var grid1 = new DnDGrid({
                        store: testCountryStore,
                        columns: [
                            {label: "Name", field:"name", sortable: false},
                            {label:"Type", field:"type", sortable: false},
                            {label:"Population", field:"population"},
                            {label:"Timezone", field:"timezone"}
                        ]
                    }, "grid1");
                    var grid2 = new DnDGrid({
                        store: testCountryStore,
                        query: {type: "country"},
                        columns: [
                            tree({label: "Name", field:"name", sortable: false}),
                            {label:"Type", field:"type", sortable: false},
                            {label:"Population", field:"population"},
                            {label:"Timezone", field:"timezone"}
                        ]
                    }, "grid2");

                    var anotherTargetDiv = dojo.byId("another-target");
                    var target = new DnDSource(anotherTargetDiv, {accept:["dgrid-row"], isSource:false});
                });
            }
    );
```