toElement: function() {                       // this.element = #tabs.tabs
  this.element = $a(                          // insert A into #tabs.tabs
    { 'class': 'tab', 'href': '#' },          // new A attributes
    $span(this.caption),                      // insert SPAN into new A; content from data-caption
    $img(                                     // insert IMG into new A
      { 'src': '/images/admin/tab_close.png', // new IMG attributes
        'class': 'close',                     // ...
        'alt': 'Remove part',                 // ...
        'title': 'Remove part'                // ...
      }
    )
  );
  return this.element;
}