code: function () {
                      this._closeTooltip();
                      var firePreviewChange = true;
                      if (this._tentativeRating <= 0) {
                          firePreviewChange = false;
                      } else {
                          if (this._tentativeRating > 0) {
                              this._tentativeRating--;
                          } else if (this._tentativeRating === -1) {
                              if (this._userRating !== 0) {
                                  if (this._userRating > 0) {
                                      this._tentativeRating = this._userRating - 1;
                                  } else {
                                      this._tentativeRating = 0;
                                  }
                              } else {
                                  this._tentativeRating = 0;
                              }
                          }
  
                          if ((this._tentativeRating === 0) && !this._enableClear) {
                              this._tentativeRating = 1;
                              firePreviewChange = false;
                          }
                      }
  
                      this._showTentativeRating(firePreviewChange, "keyboard");
                  }
docs: decrement tentative rating by one