code: function (scrollBy, animation) {
              var pages = this.pages,
                pageCount = pages.length,
                currentPage = this.currentPage + scrollBy,
                clipHeight = this.clipHeight,
                navOptions = this.options.navigation,
                activeColor = navOptions.activeColor,
                inactiveColor = navOptions.inactiveColor,
                pager = this.pager,
                padding = this.padding,
                scrollOffset;
  
              // When resizing while looking at the last page
              if (currentPage > pageCount) {
                  currentPage = pageCount;
              }
  
              if (currentPage > 0) {
  
                  if (animation !== UNDEFINED) {
                      setAnimation(animation, this.chart);
                  }
  
                  this.nav.attr({
                      translateX: padding,
                      translateY: clipHeight + this.padding + 7 + this.titleHeight,
                      visibility: VISIBLE
                  });
                  this.up.attr({
                        fill: currentPage === 1 ? inactiveColor : activeColor
                    })
                    .css({
                        cursor: currentPage === 1 ? 'default' : 'pointer'
                    });
                  pager.attr({
                      text: currentPage + '/' + pageCount
                  });
                  this.down.attr({
                        x: 18 + this.pager.getBBox().width, // adjust to text width
                        fill: currentPage === pageCount ? inactiveColor : activeColor
                    })
                    .css({
                        cursor: currentPage === pageCount ? 'default' : 'pointer'
                    });
  
                  scrollOffset = -pages[currentPage - 1] + this.initialItemY;
  
                  this.scrollGroup.animate({
                      translateY: scrollOffset
                  });
  
                  this.currentPage = currentPage;
                  this.positionCheckboxes(scrollOffset);
              }
  
          }
docs: Scroll the legend by a number of pages
  @param {Object} scrollBy
  @param {Object} animation