code: function(models, options) {
        var i, l, index, model;
        options || (options = {});
        models = _.isArray(models) ? models.slice() : [models];
        for (i = 0, l = models.length; i < l; i++) {
          model = this.getByCid(models[i]) || this.get(models[i]);
          if (!model) continue;
          delete this._byId[model.id];
          delete this._byCid[model.cid];
          index = this.indexOf(model);
          this.models.splice(index, 1);
          this.length--;
          if (!options.silent) {
            options.index = index;
            model.trigger('remove', model, this, options);
          }
          this._removeReference(model);
        }
        return this;
      }
docs: Remove a model, or a list of models from the set. Pass silent to avoid firing the `remove` event for every model removed.