docs: def funda(
          self,
          fields=None,
          min_volume=0,
          min_discount=0,
          ignore_nodown=False,
          forever=False,
      ):
          """以字典形式返回分级A数据
          :param fields:利率范围，形如['+3.0%', '6.0%']
          :param min_volume:最小交易量，单位万元
          :param min_discount:最小折价率, 单位%
          :param ignore_nodown:是否忽略无下折品种,默认 False
          :param forever: 是否选择永续品种,默认 False
          """
          if fields is None:
              fields = []
  
          # 添加当前的ctime
          self.__funda_url = self.__funda_url.format(ctime=int(time.time()))
          # 请求数据
          rep = requests.get(self.__funda_url)
          # 获取返回的json字符串
          fundajson = json.loads(rep.text)
          # 格式化返回的json字符串
          data = self.formatfundajson(fundajson)
          # 过滤小于指定交易量的数据
          if min_volume:
              data = {
                  k: data[k]
                  for k in data
                  if float(data[k]["funda_volume"]) > min_volume
              }
          if len(fields):
              data = {
                  k: data[k]
                  for k in data
                  if data[k]["coupon_descr_s"] in "".join(fields)
              }
          if ignore_nodown:
              data = {
                  k: data[k]
                  for k in data
                  if data[k]["fund_descr"].find("无下折") == -1
              }
          if forever:
              data = {
                  k: data[k]
                  for k in data
                  if data[k]["funda_left_year"].find("永续") != -1
              }
          if min_discount:
              data = {
                  k: data[k]
                  for k in data
                  if float(data[k]["funda_discount_rt"][:-1]) > min_discount
              }
  
          self.__funda = data
          return self.__funda