Collection#indexOf

    // Get the model's index by id or fall back to underscore's method
    indexOf: function(sought) {
      if (typeof sought === "string") {
        if (!this._byId[sought]) {
          return -1;
        };
        if (_.indexOf.call(_, this.pluck('id'), sought) !== -1) {
          return _.indexOf.call(_, this.pluck('id'), sought)
        } 
        return _.pluck(this.models, 'cid').indexOf(sought)
      } else {
        return _.indexOf.call(_, this.models, sought);
      }
    }