code: function createList (isCollapsed) {
      var listElement = (options.orderedList) ? 'ol' : 'ul'
      var list = document.createElement(listElement)
      var classes = options.listClass +
        SPACE_CHAR + options.extraListClasses
      if (isCollapsed) {
        classes += SPACE_CHAR + options.collapsibleClass
        classes += SPACE_CHAR + options.isCollapsedClass
      }
      list.setAttribute('class', classes)
      return list
    }
docs: Create list element.
  @param {Boolean} isCollapsed
  @return {HTMLElement}