Knockout-Kendo custom binding for a bullet graph HTML helper

kendoBullet.js

ko.bindingHandlers.kendoBullet = {
    init: function (element, valueAccessor, 
                    allBindingsAccessor, viewModel, bindingContext) {
        var options = ko.utils.unwrapObservable(valueAccessor());

        options.type = 'bullet';
        
        if (!options.chartArea) {
            options.chartArea = {};
        }
        
        if (!options.chartArea.background) {
            options.chartArea.background = 'gainsboro';
        }
        
        if (!options.tooltip) {
            options.tooltip = { template: 'Target: #= value.target #<br /> Actual: #= value.current #' };
        }
        
        if (!options.series[0].target) {
            options.series[0].target = { color: 'black' };
        }
        
        if (!options.series[0].gap) {
            options.series[0].gap = 0;
        }

        ko.bindingHandlers.kendoSparkline.init(element, ko.observable(options), 
            allBindingsAccessor, viewModel, bindingContext);
    }
};