_hydrate(records, modelName) {
    if (Array.isArray(records)) {
      let models = records.map(function (record) {
        return this._instantiateModel(modelName, record);
      }, this);
      return new Collection(modelName, models);
    } else if (records) {
      return this._instantiateModel(modelName, records);
    } else {
      return null;
    }
  }
Takes a record and returns a model, or an array of records
    and returns a collection.

    @method _hydrate
    @param records
    @param modelName
    @private
    @hide