$(document).ready(function() {
    var idCountry = $('#id_country').ninjaSelect({
        url: '/get/country/',
        itemsPerPage: 10
    });
    
    var plugin = idCountry.data().ninjaSelect;
        plugin.options.data = {
            city: '1'
        };
    
    $('#id_theme').ninjaSelect({
        url: '/get/theme/',
        itemsPerPage: 10
    });
})