docs: function (startIndex, endIndex) {
                  if (_.isUndefined(startIndex)) {
                      startIndex = Number.MAX_VALUE;
                  }
                  if (_.isUndefined(endIndex)) {
                      endIndex = -1;
                  }
                  var renderer;
                  // release unused renderer
                  for (var index in this.$activeRenderer) {
                      if (this.$activeRenderer.hasOwnProperty(index) && (index < startIndex || index > endIndex)) {
                          // render not in use
                          renderer = this.$activeRenderer[index];
                          if (renderer) {
                              renderer.set({
                                  $index: null,
                                  $dataItem: null
                              });
  
                              renderer.remove();
  
                              this.$availableRenderer.push(renderer);
                          }
  
                          delete this.$activeRenderer[index];
                      }
                  }
              }