code: function(items){
        var delta = this.set(items) || {};
        var deleted = delta.deleted;
  
        Dataset.setAccumulateState(true);
        if (deleted)
          for (var i = 0, object; object = deleted[i]; i++)
            object.destroy();
        Dataset.setAccumulateState(false);
  
        return delta.inserted;
      }
docs: Set new item set and destroy deleted items.
  @param {Array.<basis.data.Object>} items
  @return {Array.<basis.data.Object>|undefined} Returns array of inserted items or undefined if nothing inserted.