code: function (model, options, eventName) {
          var newModels = slice.call(this.models);
          var comparator = this.comparator || this.collection.comparator;
          //Whether or not we are to expect a sort event from our collection later
          var sortable = eventName === 'add' && this.collection.comparator && (options.at == null) && options.sort !== false;
          if (!sortable) {
              var index = sortedIndexBy(newModels, model, comparator);
              newModels.splice(index, 0, model);
          } else {
              newModels.push(model);
              if (options.at) newModels = this._sortModels(newModels);
          }
  
          this.models = newModels;
          this._addIndex(this._indexes, model);
          if (this.comparator && !sortable) {
              this.trigger('sort', this);
          }
      }
docs: Add a model to this filtered collection that has already passed the filters