docs: function decorate(source, constr) {
      var elements;
      if (typeof source == 'string')
        elements = tr.doc.querySelectorAll(source);
      else
        elements = [source];
  
      for (var i = 0, el; el = elements[i]; i++) {
        if (!(el instanceof constr))
          constr.decorate(el);
      }
    }