I try to achieve stacked bar chart with round border as goal design

here is what I try with the sandbox

    theme: {
      overrides: {
        bar: {
          series: {
            fillOpacity: 0.8,
            cornerRadius: 8,
            itemStyler: (s) => {
              if (s.yKey == "iphone") {
                return {
                  cornerRadius: 999,
                  fillOpacity: 0.1,
                  fill: "#cf5200",
                };
              }
            },
          },
        },
      },
    },

the cornerRadius inside itemStyler is not doing anything