docs: function(dimension, used, label, path, pathCollector, valueToNumCollector, numToValueCollector) {
          for(var key in dimension) {
              var currentPath;
              if(used[key]) {
                  used[key] = 2;
                  currentPath = path.concat(label);
              } else {
                  currentPath = path;
              }
              if(currentPath.length > 1) {
                  pathCollector.push(currentPath);
                  numToValueCollector.push(key);
                  valueToNumCollector[key] = label++;
              }
              if(dimension[key] !== null) {
                  label = this._dimensionWalk(dimension[key], used, label, currentPath,
                      pathCollector, valueToNumCollector, numToValueCollector);
              }
          }
          return label;
      }