code: function(index){
          var fieldName = this.fieldOrder[index];
          if (!fieldName)
              Xmla.Exception._newError(
                  "INVALID_FIELD",
                  "Xmla.Rowset.fieldDef",
                  index
              )._throw();
          return fieldName;
      }
docs: Retrieves the name of a field by field Index.
  Field indexes start at 0.
  @method fieldName
  @param {string} name The name of the field for which you want to retrieve the index.
  @return {int} The ordinal position (starting at 0) of the field that matches the argument.