AccountsTemplates checkbox field

Actually I’m having a minor trouble of generating checkbox in signup form. This is my present code

    _id: 'position',
    type: 'select',
    displayName: 'Role',
    select: [
        text: 'Developer',
        value: 'Developer'
        text: 'Designer',
        value: 'Designer'
        text: 'Tester',
        value: 'tester'

Below shown is my user interface

How to show these options as checkbox values instead of dropdown box, so that the user can select multiple values. I want to store that values as a list in the user’s database. Thanks in advance.

Note : I already referred the offical guide - But they didn’t provide example for multiple values. They just showed on how to use checkbox as consent.

    _id: "mailing_list",
    type: "checkbox",
    displayName: "Subscribe me to mailing List",