code: public function freeCardSummary($from, $to, $condSource = 0, $cardId = '')
      {
          $ext = [
              'cond_source' => intval($condSource),
              'card_id' => $cardId,
          ];
  
          return $this->query(self::API_FREE_CARD_SUMMARY, $from, $to, $ext);
      }
docs: 获取免费券数据接口.
  
  @param string $from
  @param string $to
  @param int    $condSource
  @param string $cardId
  
  @return \EasyWeChat\Support\Collection