customising filter module

-- url of the page with the problem -- : working locally
-- HikaShop version -- : HikaShop 2.6.3
-- Joomla version -- : 3.5.1
-- PHP version -- : 7
-- Browser(s) name and version -- : firefox 46.0.1
-- Error-message(debug-mod must be tuned on) -- : n/a

Hi
I want to customise the filter module and make it into an accordion - was wondering where I could find the relevant file to do this myself?

Can only find the following code in the template override

<div class="hikashop_filter_module">
<?php echo $html;?>
<div style="clear:both;"></div>
</div>

Ok - I got that!

Now I think I'm looking for the actual code which renders the checkboxes

<?php echo '<div class="hikashop_filter_'.$filters[$count]->filter_namekey.'">'.$html[$count].'</div>'; ?>

<div class="hikashop_filter_Country_1">
<span class="hikashop_filter_title">Country</span>
<br>
<span id="filter_values_container_Country_1_module_100" class="filter_values_container">