How to use the nvchecker.source.httpclient.DEFAULT_USER_AGENT function in nvchecker

if proxy:
      del kwargs['proxy']
    elif hasattr(self, 'nv_config') and self.nv_config.get('proxy'):
      proxy = self.nv_config.get('proxy')
    if proxy:
      host, port = proxy.rsplit(':', 1)
      kwargs['proxy_host'] = host
      kwargs['proxy_port'] = int(port)

    params = kwargs.get('params')
    if params:
      del kwargs['params']
      q = urlencode(params)
      url += '?' + q

    kwargs.setdefault("headers", {}).setdefault('User-Agent', DEFAULT_USER_AGENT)
    r = HTTPRequest(url, **kwargs)
    return ResponseManager(r)

async def _request(self, *args, **kwargs):
        if hasattr(self, "nv_config") and self.nv_config.get("proxy"):
            kwargs.setdefault("proxy", self.nv_config.get("proxy"))

        kwargs.setdefault("headers", {}).setdefault('User-Agent', DEFAULT_USER_AGENT)

        res = await super(BetterClientSession, self)._request(
            *args, **kwargs)
        if res.status >= 400:
            raise HTTPError(res.status, res.reason, res)
        return res

def setup_session(proxy: Optional[str], concurrency: int):
  s = httpx.AsyncClient(
    pool_limits = httpx.PoolLimits(
      soft_limit = concurrency * 2,
      hard_limit = concurrency,
    ),
    timeout = httpx.Timeout(20, pool_timeout=None),
    headers = {'User-Agent': DEFAULT_USER_AGENT},
    http2 = True,
    proxies = proxy,
  )
  session.set(Session(s, concurrency))