function getRequired(element) {
        var elementRole = axs.utils.getRoles(element);
        if (!elementRole || !elementRole.applied)
            return [];
        var appliedRole = elementRole.applied;
        if (!appliedRole.valid)
            return [];
        return appliedRole.details['mustcontain'] || [];
    }
Get a list of the roles this element must contain, if any, based on its ARIA role.
@param {Element} element A DOM element.
@return {Array.<string>} The roles this element must contain.