code: public GetDepartmentListResponse getList(Integer parentId){
          GetDepartmentListResponse response;
          String url;
          if(parentId != null) {
              url = BASE_API_URL + "cgi-bin/department/list?access_token=#&id=" + parentId;
          }else{
              url = BASE_API_URL + "cgi-bin/department/list?access_token=#";
          }
          BaseResponse r = executeGet(url);
          String resultJson = isSuccess(r.getErrcode()) ? r.getErrmsg() : r.toJsonString();
          response = JSONUtil.toBean(resultJson, GetDepartmentListResponse.class);
          return response;
      }
docs: 获取部门列表
  @param parentId 父级部门ID。可不填，不填表示顶级部门
  @return 部门列表