301     for(let index of this.indexes){

   301     for(let index of this.indexes){

   302         subscribers[index + new_offset].add(this);

   302         subscribers[index + new_offset].add(this);

   303     }

   303     }

   304 }

   304 }

   305 

   305 

   307     for(let item of this.items){

   307     for(let item of this.items){

   308         for(let widget of item) {

   308         for(let widget of item) {

   309             unsubscribe.call(widget);

   309             unsubscribe.call(widget);

   310         }

   310         }

   311     }

   311     }

   312 }

   312 }

   313 

   313 

   315     for(let i = 0; i < this.items.length; i++) {

   315     for(let i = 0; i < this.items.length; i++) {

   316         let item = this.items[i];

   316         let item = this.items[i];

   317         let orig_item_index = this.index_pool[i];

   317         let orig_item_index = this.index_pool[i];

   318         let item_index = this.index_pool[i+this.item_offset];

   318         let item_index = this.index_pool[i+this.item_offset];

   319         let item_index_offset = item_index - orig_item_index;

   319         let item_index_offset = item_index - orig_item_index;