def fileDescriptorReceived(self, descriptor):
        """
        Fire the waiting Deferred, initialized by C{waitForDescriptor}, with the
        file descriptor just received.
        """
        self.waiting.callback(descriptor)
        self.waiting = None

        Fire the waiting Deferred, initialized by C{waitForDescriptor}, with the
        file descriptor just received.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_unix.py