code: function(hierarchyIndexOrName){
          if (_isUnd(hierarchyIndexOrName)) index = this._hierarchyIndex;
          var index, hierarchyName, hierarchy;
          if (_isNum(hierarchyIndexOrName)) {
              if (hierarchyIndexOrName !== parseInt(hierarchyIndexOrName, 10)
              ||  hierarchyIndexOrName >= this.numHierarchies
              )
                  Xmla.Exception._newError(
                      "INVALID_HIERARCHY",
                      "Xmla.Dataset.Axis.hierarchyDef",
                      hierarchyIndexOrName
                  )._throw();
              hierarchyName = this.hierarchyName(hierarchyIndexOrName);
          }
          else hierarchyName = hierarchyIndexOrName;
          hierarchy = this._hierarchyDefs[hierarchyName];
          if (_isUnd(hierarchy))
              Xmla.Exception._newError(
                  "INVALID_HIERARCHY",
                  "Xmla.Dataset.Axis.hierarchyDef",
                  hierarchyName
              )._throw();
          return hierarchy;
      }
docs: Gets the hierarchy identified by the specified index or hierarchyName, or the current hierarchy (in case the argument is omitted).
  The hierarchy is returned as an object with the following properties:<ul>
  <li>index {int} Integer indicating the ordinal position of this hiearchy within the axis.</li>
  <li>name {string} String that holds the name of this hierarchy.</li>
  </ul>
  In addition, the XML/A specification suggests the following standard properties:<ul>
  <li>UName {string} the unique name of this hierarchy</li>
  <li>Caption {string} the human friendly name for this hierarchy</li>
  <li>LName {string} the level name</li>
  <li>LNum {int} the level number</li>
  <li>DisplayInfo {int} displayinfo</li>
  </ul>
  @method hierarchy
  @param hierarchyIndexOrName {int|string} The ordinal or name of the hierarchy that is to be retrieved. When omitted, the the current hierarchy is returned.
  @return {string} The hierarchy specified by the argument index or name, or the current hierarchy if the argument is omitted.