def resolutionBegan(self, hostResolution):
        """
        Hostname resolution began.

        @param hostResolution: see L{IResolutionReceiver}
        """
        self._started = True
        self._resolution = hostResolution
        self._addresses = []

        Hostname resolution began.

        @param hostResolution: see L{IResolutionReceiver}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_resolver.py