docs: function () {
              if (this.__stackCache) {
                  for (var key in this.__stackCache) {
                      if (this.__stackCache.hasOwnProperty(key)) {
                          var stack = this.__stackCache[key];
                          // break dom reference
                          for (var i = 0, l = stack.length; i < l; i++) {
                              stack.target = null;
                              stack.expandoValue = null;
                              delete stack.target;
                              delete stack.expandoValue;
                          }
                          delete this.__stackCache[i];
                      }
                  }
                  this.__stackCache = null;
              }
          }