I have this html accordion code:

<div class="accordion_container">
    <div class="container">

        <div class="accordion">
            <button class="header">
                Úvod
                <i class="icon"></i>
            </button>
            <div class="body">
                Lorem Ipsum
            </div>

        </div>
        <div class="accordion">
            <button class="header">
                Závěr
                <i class="icon"></i>
            </button>
            <div class="body">
                Lorem Ipsum
            </div>
        </div>
    </div>

and this script:

    <script>
let accordion_btns  = document.querySelectorAll('.accordion_container .accordion .header'),
    accordion_bodys = document.querySelectorAll('.accordion_container .accordion .body');

if(accordion_btns && accordion_bodys)
{
    accordion_btns = Array.isArray(accordion_btns) ? accordion_btns : Object.values(accordion_btns);
    accordion_btns.forEach(accordion_btn=>{
        accordion_btn.addEventListener('click', function(){
            process_accordion(this);
        });
    });

    function process_accordion(x) {
        set_height_0();

        let next_sibling = x.nextElementSibling;
        if(next_sibling.offsetHeight>0)
        {
            next_sibling.style.height = '0px';
            x.closest('.accordion').classList.remove('active');
        } else {
            next_sibling.style.height = next_sibling.scrollHeight+30+'px';
            x.closest('.accordion').classList.add('active');
        }
    }

    function set_height_0() {
        accordion_bodys = Array.isArray(accordion_bodys) ? accordion_bodys : Object.values(accordion_bodys);
        accordion_bodys.forEach(accordion_body=>{
            accordion_body.style.height = '0px';
            accordion_body.closest('.accordion').classList.remove('active');
        });
    }
}
</script>

I was trying from all my strengh and using all my beginner brain power, but I can't figure out, how to modify this code so the first accordion is active when I load the page. I tried adding the active class to into the html but the only part of the accordion is open when i load the page.