code: function () {
              var seriesMarkerOption = this.options.marker;
  
              this.getCyclic('symbol', seriesMarkerOption.symbol, this.chart.options.symbols);
  
              // don't substract radius in image symbols (#604)
              if (/^url/.test(this.symbol)) {
                  seriesMarkerOption.radius = 0;
              }
          }
docs: Get the series' symbol