How to add onChange method for uiselectmultiple element in angular-schema-form

I can add multiple items into a dropdown in angular schema form using the following schema and form.

var schema = {
    "type": "object",
    "properties": {
        "model": {
            "type": "string"
        }
    }
}

var form = [
    {
        key: "model",
        type: "uiselectmultiple",
        titleMap: {
            "Model 1", "model_1",
            "Model 2", "model_2",
            "Model 3", "model_3"
        },
        onChange: changeValues(modelValue, form)
    }   
];

onChange method doesn't fire when selecting an item from the list. Followed this solution and didn't get the expected result. http://ift.tt/2xyge9h

Anyone knows the answer for this problem. I can use checkboxes instead of using multi-selection. But how to remove the "X" mark, "+add" button and additional header text from the checkboxes.

var form = [
    {
        key: "comment",
        onChange: function(model, form){
            console.log('got there though');
        }    
    }
];