code: function(models, options) {
        var singular = !Array.isArray(models);
        models = singular ? [models] : models.slice();
        options || (options = {});
        for (var i = 0, length = models.length; i < length; i++) {
          var model = models[i] = this.get(models[i]);
          if (!model) continue;
          var id = this.modelId(model.attributes);
          if (id != null) delete this._byId[id];
          delete this._byId[model.cid];
          var 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, options);
        }
        return singular ? models[0] : models;
      }
docs: Remove a model, or a list of models from the set.