code: public RefundApplyResponse apply(RefundApplyRequest request){
          checkApplyParams(request);
          Map<String, String> applyParams = buildApplyParams(request);
          return doHttpsPost(APPLY, applyParams, RefundApplyResponse.class);
      }
docs: 申请退款
  @param request 退款请求对象
  @return RefundResponse对象，或抛WepayException