docs: function(item) {
        var self = this;
        var items = Array.isArray(item) ? item : [item];
        var added = false;
        _.each(items, function(item) {
          if(!_.contains(self.items, item)) {
            self.items.push(item);
            if(item && item.klass == 'Instance') {
              item.once('delete', function() {
                self.remove(item);
              });
            };
            added = true;
          }
        });
        if(added) {
          self.emit('add');
          self.emit('change:size');
          self.emit('change');
        }
        return self;
      }