var multipleOpenAccordion = new Class({
  Extends: Accordion,
  options: {
    allowMultipleOpen: true,
    display: -1
  },
  initialize: function(togglers,togglees,options){
    this.parent(togglers,togglees,this.options);
  },
  display: function(index){
    index = ($type(index) == 'element') ? this.elements.indexOf(index) : index;
    if ((this.timer && this.options.wait) || (index === this.previous && !this.options.alwaysHide)) return this;
    
    var obj = {};
    if(this.options.allowMultipleOpen){
      var el = this.elements[index];
      obj[index] = {};
      var hide = (el.offsetHeight > 0);
      this.fireEvent(hide ? 'onBackground' : 'onActive', [this.togglers[index], el]);
      for (var fx in this.effects) obj[index][fx] = hide ? 0 : el[this.effects[fx]];
    }else{
      this.previous = index;
      this.elements.each(function(el, i){
        obj[i] = {};
        var hide = (i != index) || (this.options.alwaysHide && (el.offsetHeight > 0));
        this.fireEvent(hide ? 'onBackground' : 'onActive', [this.togglers[i], el]);
        for (var fx in this.effects) obj[i][fx] = hide ? 0 : el[this.effects[fx]];
      }, this);
      
    }
    return this.start(obj);
  }
});