docs: function (evt, callback) {
      if (this.id && dotty.exists(evt, this.id)) {
        debug('found viewmodel id in event');
        return callback(null, dotty.get(evt, this.id));
      }
  
      if (this.getNewIdForThisEventExtender) {
        debug('[' + this.name + '] found eventextender id getter in event');
        return this.getNewIdForThisEventExtender(evt, callback);
      }
      
      debug('not found viewmodel id in event, generate new id');
      this.collection.getNewId(callback);
    }