def shutdown_kernel(self, restart=False):
        """ Attempts to the stop the kernel process cleanly. If the kernel
        cannot be stopped, it is killed, if possible.
        """
        # FIXME: Shutdown does not work on Windows due to ZMQ errors!
        if sys.platform is not 'win32':
            self.kill_kernel()
            return

        # Don't send any additional kernel kill messages immediately, to give
        # the kernel a chance to properly execute shutdown actions. Wait for at
        # most 1s, checking every 0.1s.
        self.xreq_channel.shutdown(restart=restart)
        for i in range(10):
            if self.is_alive:
                time.sleep(0.1)
            else:
                break
        else:
            # OK, we've waited long enough.
            if self.has_kernel:
                self.kill_kernel()
dataset/ETHPy150Open ipython/ipython-py3k/IPython/parallel/engine/kernelstarter.py/KernelStarter.shutdown_kernel/operator `==` -> `is not`