Kendo Treelist: Transport Update shows options.model as undefined and hence returns nothing

I am working with Kendo Editable TreeList (with angular). I am trying to use the "transport" functionality to communicate with my remote service. While the read works fine (i.e. I get the JSON data and am able to render it correctly), the update functionality does not work correctly. To be specific, the options.models remains "undefined" and as a result nothing is sent back.

I ran the angular treelist example on kendo website in DOJO and the options.model there turns out to be undefined as well. (you can run it by editing the example here: http://demos.telerik.com/kendo-ui/treelist/angular)

What follows below is the code I am working with (which is similar to the one provided in the telerik's example in the above link)

Can someone please tell me what I might be doing wrong here?

Thanks a lot!

        vm.treelistOptions = {
            dataSource: {
                    transport: {
                        read:{
                            url: myURL,
                            dataType:"json"
                        },
                        update: {
                            url: myURL + "update",
                            dataType: "json",
                            type: "post"
                        },
                        parameterMap: function(options, operation) {
                                if (operation == "read") {
                                    console.log("Transport READ works");
                                }
                                if (operation == "update"){
                                    console.log("Transport UPDATE works");
                                    console.log(options.models);
                                }
                                if (operation !== "read" && options.models) {
                                    console.log("reached inside the IF in parammap");
                                    return {models: JSON.stringify(options.models)};
                                }
                            }

                    },
                schema: {
                    model: {
                        id: "stId",
                        parentId: "stLink",
                        fields: {
                            stId: {type: "number", editable: false, nullable: false},
                            stLink: {nullable: true, type: "number"},
                            stName: {validation: {required: true}},
                            v: {type: "number", editable:true}
                        }
                    }
                }
            },
            sortable:true,
            editable:true,
            columns: [
                { field: "stName", title: "st", width: "150px" },
                { field: "v", title: "Ex v", width: "150px" },
                { command: ["edit"] }
            ]

        }

After a bit of a research and comparing non-angular v/s angular examples on Kendo, I figured their angular example with parameterMap was missing the batch=True option. This goes right after transport and just before schema section in the comparable non-angular example...which seems to fix the issue