code: public Legend selected(String name, Boolean selected) {
          if (!this.data.contains(name)) {
              throw new RuntimeException("Legend中不包含name为" + name + "的图例");
          }
          if (this.selected == null) {
              this.selected = new LinkedHashMap<String, Boolean>();
          }
          this.selected.put(name, selected);
          return this;
      }
docs: 设置默认选中状态
  
  @param name
  @param selected
  @return