var group_by_file = (function(){
  var grouped_by_file = false

  return function(){
    var sw = TreeHtmlGroup({
      name: 'by_file',
      key: function get_path(li) {
        var p = li.querySelector('a').innerText.replace(/.*\s(.*):\d+/, '$1')
        if (p === '') {
          var callees = li.querySelector('ul')
          if (callees !== null) {
            return get_path(callees.children[0])
          }
        }
        return '<b>' + p + '</b>'
      }
    })

    sw(grouped_by_file ? '' : 'by_file')
    grouped_by_file = !grouped_by_file
  }
})()