docs: function (e) {
                  var keyCode = e.domEvent.keyCode;
                  if (keyCode === 38 || keyCode === 40 || keyCode === 37 || keyCode === 39) {
                      var index = this.$currentSelectionIndex !== null ? this.$currentSelectionIndex : -1;
                      var indexOffset;
                      if (this.$.scrollDirection === SCROLL_DIRECTION_VERTICAL) {
                          indexOffset = this.$._cols;
                      } else {
                          indexOffset = this.$._rows;
                      }
                      switch (keyCode) {
                          case 38:
                              index -= this.$._cols;
                              break;
                          case 40:
                              index += this.$._cols;
                              break;
                          case 37:
                              index--;
                              break;
                          case 39:
                              index++;
                              break;
                          default:
                              void 0;
                      }
                      if (index < 0) {
                          index = 0;
                      }
                      if (this.$.$dataAdapter && index >= this.$.$dataAdapter.size()) {
                          index = this.$.$dataAdapter.size() - 1;
                      }
                      this._selectItem(index, e.domEvent.shiftKey, false);
                      e.preventDefault();
                      e.stopPropagation();
                  }
              }