How to use the pycares.QUERY_TYPE_NS function in pycares

def test_query_ns(self):
        self.result, self.errorno = None, None
        def cb(result, errorno):
            self.result, self.errorno = result, errorno
        self.channel.query('google.com', pycares.QUERY_TYPE_NS, cb)
        self.wait()
        self.assertNoError(self.errorno)
        for r in self.result:
            self.assertEqual(type(r), pycares.ares_query_ns_result)

def __init__(self, domain, query_type, ttl, answer):
        """
        :param domain: 域名
        :type domain: str
        :param query_type: 记录类型
        :type query_type: int
        :param ttl: 生存时间
        :type ttl: int
        :param answer: 请求结果
        :type answer: list
        """
        self.domain = domain

        if query_type not in (QUERY_TYPE_NS, QUERY_TYPE_A, QUERY_TYPE_CNAME):
            raise ValueError('query_type must be one of QUERY_TYPE_NS, QUERY_TYPE_A or QUERY_TYPE_CNAME')

        self.type = query_type
        self.ttl = ttl
        self.answer = answer if answer else []

__version__ = '2.0.0'

__all__ = ('DNSResolver', 'error')


READ = 1
WRITE = 2

query_type_map = {'A'     : pycares.QUERY_TYPE_A,
                  'AAAA'  : pycares.QUERY_TYPE_AAAA,
                  'ANY'   : pycares.QUERY_TYPE_ANY,
                  'CNAME' : pycares.QUERY_TYPE_CNAME,
                  'MX'    : pycares.QUERY_TYPE_MX,
                  'NAPTR' : pycares.QUERY_TYPE_NAPTR,
                  'NS'    : pycares.QUERY_TYPE_NS,
                  'PTR'   : pycares.QUERY_TYPE_PTR,
                  'SOA'   : pycares.QUERY_TYPE_SOA,
                  'SRV'   : pycares.QUERY_TYPE_SRV,
                  'TXT'   : pycares.QUERY_TYPE_TXT
        }


class DNSResolver:
    def __init__(self, nameservers: Optional[List[str]] = None, loop: Optional[asyncio.AbstractEventLoop] = None,
                 **kwargs: Any) -> None:
        self.loop = loop or asyncio.get_event_loop()
        assert self.loop is not None
        kwargs.pop('sock_state_cb', None)
        self._channel = pycares.Channel(sock_state_cb=self._sock_state_cb, **kwargs)
        if nameservers:
            self.nameservers = nameservers