code: async def verify_permissions(self, user_id, *permissions):
          
  
          prefix = f"{self._prefix_perm}/{user_id}/"
  
          perm_names = [str(p) for p in permissions]
          
          checkings = [KV.get.txn(prefix + p) for p in perm_names]
          success, responses = await self._client.txn(compare=[], success=checkings)
          if not success:
              errmsg = f"无法读取用户({user_id})的权限信息"
              raise Unprocessable(errmsg)
  
          for i, item  in enumerate(responses):
              if item[0] is not None:
                  return permissions[0]
                  
          return None
docs: 返回当前用户所匹配的首个有效权限