code: function(index, range) {
          if(!lang.isNumber(range) || (range < 0)) {
              range = 1;
          }
          this._records.splice(index, range);
          //this._length = this._length - range;
      }
docs: Deletes Records from the RecordSet at the given index. If range is null,
  then only one Record is deleted.
  
  @method _deleteRecord
  @param index {Number} Position index.
  @param range {Number} (optional) How many Records to delete
  @private