class_docstr: Name resolver based on the c-ares library.
  
  This is a non-blocking and non-threaded resolver.  It may not produce
  the same results as the system resolver, but can be used for non-blocking
  resolution when threads cannot be used.
  
  c-ares fails to resolve some names when ``family`` is ``AF_UNSPEC``,
  so it is only recommended for use in ``AF_INET`` (i.e. IPv4).  This is
  the default for ``tornado.simple_httpclient``, but other libraries
  may default to ``AF_UNSPEC``.
  
  .. versionchanged:: 4.1
     The ``io_loop`` argument is deprecated.
code: def initialize(self, io_loop=None):
      self.io_loop = io_loop or IOLoop.current()
      self.channel = pycares.Channel(sock_state_cb=self._sock_state_cb)
      self.fds = {}
  
file_path: catboost/contrib/python/tornado/tornado-4/tornado/platform/caresresolver.py
imports: from __future__ import absolute_import, division, print_function
  import pycares
  import socket
  from tornado import gen
  from tornado.ioloop import IOLoop
  from tornado.netutil import Resolver, is_valid_ip
label_desc: Use image node_id 1 for calling the CaresResolver obj's underlying member method code with example usage: obj.initialize(io_loop) without return types