code: def get_symbols(self, site='Pro', _async=False):
          
          assert site in ['Pro', 'HADAX']
          params = {}
          path = f'/v1{"/" if site == "Pro" else "/hadax/"}common/symbols'
          return api_key_get(params, path, _async=_async)
docs: 获取  支持的交易对
          :param site:
          :return: