def _execute(self):
        """
        Callback fired when the associated event is set.  Run the C{action}
        callback on the wrapped descriptor in the main reactor thread and raise
        or return whatever it raises or returns to cause this event handler to
        be removed from C{self._reactor} if appropriate.
        """
        return blockingCallFromThread(
            self._reactor, lambda: getattr(self._fd, self._action)())

        Callback fired when the associated event is set.  Run the C{action}
        callback on the wrapped descriptor in the main reactor thread and raise
        or return whatever it raises or returns to cause this event handler to
        be removed from C{self._reactor} if appropriate.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/win32eventreactor.py