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

Question

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)
    }   
];

The onChange method doesn't fire when selecting an item from the list. I followed this solution and still didn't get the expected result.

I can use checkboxes instead of using multi-selection. But then I would have to remove the "X" mark, "+add" button and additional header text from the checkboxes. How to handle onChange with Angular Schema Form Checkbox boolean?