def __init__(self, reactor, getThreadPool=None, getaddrinfo=getaddrinfo):
        """
        Create a L{GAIResolver}.

        @param reactor: the reactor to schedule result-delivery on
        @type reactor: L{IReactorThreads}

        @param getThreadPool: a function to retrieve the thread pool to use for
            scheduling name resolutions.  If not supplied, the use the given
            C{reactor}'s thread pool.
        @type getThreadPool: 0-argument callable returning a
            L{twisted.python.threadpool.ThreadPool}

        @param getaddrinfo: a reference to the L{getaddrinfo} to use - mainly
            parameterized for testing.
        @type getaddrinfo: callable with the same signature as L{getaddrinfo}
        """
        self._reactor = reactor
        self._getThreadPool = (reactor.getThreadPool if getThreadPool is None
                               else getThreadPool)
        self._getaddrinfo = getaddrinfo

        Create a L{GAIResolver}.

        @param reactor: the reactor to schedule result-delivery on
        @type reactor: L{IReactorThreads}

        @param getThreadPool: a function to retrieve the thread pool to use for
            scheduling name resolutions.  If not supplied, the use the given
            C{reactor}'s thread pool.
        @type getThreadPool: 0-argument callable returning a
            L{twisted.python.threadpool.ThreadPool}

        @param getaddrinfo: a reference to the L{getaddrinfo} to use - mainly
            parameterized for testing.
        @type getaddrinfo: callable with the same signature as L{getaddrinfo}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/_resolver.py