function expand (i){
const expand_content=document.getElementById('expand-content-' + i);
const expand_list=document.getElementById('expand-list-' + i);
const collapse=document.getElementById('collapse' + i);
const icon=document.getElementById('icon' + i);
if(collapse.dataset.expanded=='true'){
collapse.dataset.expanded='false';
expand_content.style.maxHeight=0;
expand_content.style.transition='1s';
expand_content.style.transitionProperty='all';
expand_list.style.transition='1s'
icon.className=icon.dataset.opened;
}else{
collapse.dataset.expanded='true';
expand_content.style.transition='1s';
expand_list.style.transition='1s';
expand_content.style.transitionProperty='all';
expand_content.style.maxHeight=expand_content.scrollHeight + 'px';
icon.className=icon.dataset.closed;
}};