code: function itemY(legend, itemNumber) {
    var cumSpacingAbove = legend.items
      .slice(itemNumber)
      .reduce(function(prev, item) {
        return prev + (item.spacingAbove || 0);
      }, 0);
    return (
      (legend.items.length - itemNumber - 1) *
        (legend.computedItemHeight + legend.itemSpacing) +
      cumSpacingAbove
    );
  }
docs: /*
  The Y position of the top of a given item number, relative to the top of the bar.