code: public Option xAxis(Axis... values) {
          if (values == null || values.length == 0) {
              return this;
          }
          if (this.xAxis().size() == 2) {
              throw new RuntimeException("xAxis已经存在2个，无法继续添加!");
          }
          if (this.xAxis().size() + values.length > 2) {
              throw new RuntimeException("添加的xAxis超出了最大允许的范围:2!");
          }
          this.xAxis().addAll(Arrays.asList(values));
          return this;
      }
docs: 添加x轴
  
  @param values
  @return