addEventListener("load", addCollaps);
  function addCollaps() {
    var coll = document.getElementsByClassName("collapsible");
    for (var c of coll) {
      c.addEventListener("click", function() {
        this.nextElementSibling.classList.toggle("collapsed");
      });
    }
  }
  // TODO : kann raus
  function loadJson(filename, callback) {
    var xhr = XMLHttpRequest();
    xhr.onreadystatechange = function() {
      if(this.readyState == 4 && this.status == 200) {
        callback(JSON.parse(xhr.responseText));
      }
    }
    xhr.open(get, filename);
    xhr.send();
  }